Laser Induced Breakdown Spectroscopy for Elemental Analysis in Environmental, Cultural Heritage and Space Applications: A Review of Methods and Results
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paper_title: Laser induced breakdown spectroscopy of soils, rocks and ice at subzero temperatures in simulated martian conditions

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Abstract We applied Laser Induced Breakdown Spectroscopy (LIBS) on moist soil/rock samples in simulated Martian conditions. The signal behavior as a function of the surface temperature in the range from + 25 °C to − 60 °C was studied at pressure of 7 mbar. We observed the strong signal oscillations below 0 °C with different negative peaks, whose position, width and magnitude depend on the surface roughness. In some cases, the signal was reduced for one order of magnitude with consequences for the LIBS analytical capability. We attribute such a signal behavior to the presence of supercooled water inside the surface pores, which freezing point depends on the pore size. On a same rock samples with different grades of the surface polishing, the signal has different temperature dependence. Its decrease was always registered close to 0 °C, corresponding to the freezing/melting of normal disordered ice, which can be present inside larger pores and scratching. An amount of the signal reduction at the phase transition temperatures does not seem to change with the laser energy density in the examined range. Comparative measurements were performed on a frozen water solution. A large depression, for two orders of magnitude, of the LIBS intensity was observed close to − 50 °C. The same negative peak, but with a smaller magnitude, was also registered on some rock/soil samples. Ablation rates and plasma parameters as a function of the sample temperature are also discussed, and their consequences for in-situ analyses.
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paper_title: Study of sub-mJ-excited laser-induced plasma combined with Raman spectroscopy under Mars atmosphere-simulated conditions

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Laser-Induced Breakdown Spectroscopy (LIBS) and Raman spectroscopy are complimentary techniques. LIBS yields elemental information while Raman spectroscopy yields molecular information about a sample, and both share similar instrumentation configurations. The combination of LIBS and Raman spectroscopy in a single instrument for planetary surface exploration has been proposed, however challenges exist for developing a combined instrument. We present LIBS and Raman spectroscopy results obtained using a diode pumped, intracavity doubled, Q-switched, Nd:YLF laser operating at 523 nm, which overcomes some of the difficulties associated with a combined instrument. LIBS spectra were obtained with 170 μJ per pulse at 4 Hz repetition rate in a low pressure Mars-simulated atmosphere and Raman spectra produced with 200 mW at 100 kHz. The Nd:YLF laser is switchable between LIBS and Raman spectroscopy modes only by a change in Q-switch repetition rate. Emissions from Ca, Ca II, Fe, Fe II, Mg, Na, and O atom were identified in the μ-LIBS spectrum of oolithic hematite. Evidence was found for a change in plasma dynamics between 7 and 5 Torr that could be explained as a decrease in plasma temperature and electron density below 5 Torr. This is relevant to future Mars exploration using LIBS as the mean surface pressure on Mars varies from 3.75 to 6 Torr. LIBS plasma dynamics should be carefully evaluated at the pressures that will be encountered at the specific Mars landing site.
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paper_title: Laser-induced breakdown spectroscopy for space exploration applications: Influence of the ambient pressure on the calibration curves prepared from soil and clay samples

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Abstract Recently, there has been an increasing interest in the laser-induced breakdown spectroscopy (LIBS) technique for stand-off detection of geological samples for use on landers and rovers to Mars, and for other space applications. For space missions, LIBS analysis capabilities must be investigated and instrumental development is required to take into account constraints such as size, weight, power and the effect of environmental atmosphere (pressure and ambient gas) on flight instrument performance. In this paper, we study the in-situ LIBS method at reduced pressure (7 Torr CO 2 to simulate the Martian atmosphere) and near vacuum (50 mTorr in air to begin to simulate the Moon or asteroids' pressure) as well as at atmospheric pressure in air (for Earth conditions and comparison). Here in-situ corresponds to distances on the order of 150 mm in contrast to stand-off analysis at distance of many meters. We show the influence of the ambient pressure on the calibration curves prepared from certified soil and clay pellets. In order to detect simultaneously all the elements commonly observed in terrestrial soils, we used an Echelle spectrograph. The results are discussed in terms of calibration curves, measurement precision, plasma light collection system efficiency and matrix effects.
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paper_title: Laser induced breakdown spectroscopy on soils and rocks: Influence of the sample temperature, moisture and roughness

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Abstract ExoMars, ESA's next mission to Mars, will include a combined Raman/LIBS instrument for the comprehensive in-situ mineralogical and elemental analyses of Martian rocks and soils. It is inferred that water exists in the upper Martian surface as ice layers, “crystal” water or adsorbed pore water. Thus, we studied Laser Induced Breakdown Spectroscopy (LIBS) on wet and dry rocks under Martian environmental conditions in the temperature range − 60 °C to + 20 °C and in two pressure regimes, above and below the water triple point. Above this point, the LIBS signals from the rock forming elements have local minima that are accompanied by hydrogen (water) emission maxima at certain temperatures that we associate with phase transitions of free or confined water/ice. At these sample temperatures, the plasma electron density and its temperature are slightly lowered. In contrast to powder samples, a general increase of the electron density upon cooling was observed on rock samples. By comparing the LIBS signal behavior from the same rock with different grades of polishing, and different rocks with the same surface treatment, it was possible to distinguish between the influence of surface roughness and the bulk material structure (pores and grains). Below the triple point of water, the LIBS signal from the major sample elements is almost independent of the sample temperature. However, at both considered pressures we observed a hydrogen emission peak close to − 50 °C, which is attributed to a phase transition of supercooled water trapped inside bulk pores.
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paper_title: Detection of carbon content in a high-temperature and high-pressure environment using laser-induced breakdown spectroscopy

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Abstract A laser-induced breakdown spectroscopy (LIBS) technique has been applied to detect the carbon content in fly ash, char and pulverized coal under high-pressure and high-temperature conditions. An automated LIBS unit has been developed and applied in this experiment to demonstrate its capability in actual power plant monitoring. Gas composition effects were examined to obtain the best operating parameters under actual plant conditions. The results were compared to those obtained using the conventional method, showing satisfactory agreement. LIBS can detect carbon content even under the high-pressure conditions typical of gasification thermal power plants. LIBS is capable of a detection time of 1 min, as compared to over 30 min of sampling and analysis time required by the conventional methods (JIS-M8814 and JIS-M8815), and offers various merits as a tool for actual power-plant monitoring.
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paper_title: Rapid in-situ analysis of liquid steel by laser-induced breakdown spectroscopy☆

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Abstract Laser-induced breakdown spectroscopy (LIBS) denotes a technique where a pulsed laser beam is used to ablate small amounts of the target material. The characteristic optical emission line intensities of the excited species in the laser-generated plasma allow a quantitative chemical analysis of the target material. LIBS is a fast, non-contact method allowing large working distances between the sample under investigation and the detection system. These properties make LIBS applicable to process control in metallurgy. We describe an apparatus designed for rapid in-situ analysis of solid and molten metals at variable distances of up to 1.5 m. A variable lens system allows compensation for varying positions of the liquid steel surface. The LIBS signal is guided by a fiber optic bundle of 12-m length to the spectrometer. Analysis of an element's concentration takes 7 s. Laboratory experiments using an induction furnace showed that the addition of admixtures to liquid steel results in rapid response of the system. Results including the in-situ monitoring of Cr, Cu, Mn and Ni within certain concentration ranges are presented (Cr: 0.11–13.8 wt.%; Cu: 0.044–0.54 wt.%; Mn: 1.38–2.5 wt.%; Ni: 0.049–5.92 wt.%).
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paper_title: Real time and in situ determination of lead in road sediments using a man-portable laser-induced breakdown spectroscopy analyzer

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Abstract In situ, real time levels of lead in road sediments have been measured using a man-portable laser-induced breakdown spectroscopy analyzer. The instrument consists of a backpack and a probe housing a Q-switched Nd:YAG laser head delivering 50 mJ per pulse at 1064 nm. Plasma emission was collected and transmitted via fiber optic to a compact cross Czerny-Turner spectrometer equipped with a linear CCD array allocated in the backpack together with a personal computer. The limit of detection (LOD) for lead and the precision measured in the laboratory were 190 μg g −1 (calculated by the 3σ method) and 9% R.S.D. (relative standard deviation), respectively. During the field campaign, averaged Pb concentration in the sediments were ranging from 480 μg g −1 to 660 μg g −1 depending on the inspected area, i.e. the entrance, the central part and the exit of the tunnel. These results were compared with those obtained with flame-atomic absorption spectrometry (flame-AAS). The relative error, expressed as [100(LIBS result − flame AAS result)/(LIBS result)], was approximately 14%.
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paper_title: Double-pulse LIBS in bulk water and on submerged bronze samples

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In this work laser-induced breakdown spectroscopy (LIBS) has been applied in bulk water using a double-pulse laser source. As in the case of former experiments in air, the use of the double-pulse technique allows for enhancing line emission intensity and reducing the duration of the continuum spectrum, thus increasing the overall analytical performances of the technique. Tap water analysis of Na and Mg dissolved cations has been performed to investigate the capability of the technique, but most significant results have been obtained in determining the composition of submerged bronze targets by laser ablation of their surface in seawater. When the plasma is generated by double-pulse laser, the ablated matter is strongly confined by the water vapor inside the cavitations bubble. The confinement of the plasma leads to higher values of excitation temperature and holds the conditions suitable for chemical analysis (homogeneity and LTE) longer than what happens in gaseous media. The double-pulse experiments performed directly in bulk water point out the features of LIBS technique for real analytical applications in situ, such as the water quality assessment and the investigation of irremovable submerged objects.
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paper_title: On-line analysis of ambient air aerosols using laser-induced breakdown spectroscopy

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Abstract Laser-induced breakdown spectroscopy is developed for the detection of aerosols in ambient air, including quantitative mass concentration measurements and size/composition measurements of individual aerosol particles. Data are reported for ambient air aerosols containing aluminum, calcium, magnesium and sodium for a 6-week sampling period spanning the Fourth of July holiday period. Measured mass concentrations for these four elements ranged from 1.7 parts per trillion (by mass) to 1.7 parts per billion. Ambient air concentrations of magnesium and aluminum revealed significant increases during the holiday period, which are concluded to arise from the discharge of fireworks in the lower atmosphere. Real-time conditional data analysis yielded increases in analyte spectral intensity approaching 3 orders of magnitude. Analysis of single particles yielded composition-based aerosol size distributions, with measured aerosol diameters ranging from 100 nm to 2 μm. The absolute mass detection limits for single particle analysis exceeded sub-femtogram values for calcium-containing particles, and was on the order of 2–3 femtograms for magnesium and sodium-based particles. Overall, LIBS-based analysis of ambient air aerosols is a promising technique for the challenging issues associated with the real-time collection and analysis of ambient air particulate matter data.
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paper_title: Nanosecond and femtosecond Laser Induced Breakdown Spectroscopic analysis of bronze alloys

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Abstract In the present work we are studying the influence of pulse duration (nanosecond (ns) and femtosecond (fs)) at λ = 248 nm on the laser-induced plasma parameters and the quantitative analysis results for elements such as Sn, Zn and Pb, in different types of bronze alloys adopting LIBS in ambient atmosphere. Binary (Sn–Cu), ternary (Sn–Zn–Cu or Sn–Pb–Cu) and quaternary (Sn–Zn–Pb–Cu) reference alloys characterized by a chemical composition and metallurgical features similar to those used in Roman times, were employed in the study. Calibration curves, featuring linear regression coefficients over 98%, were obtained for tin, lead and zinc, the minor elements in the bronze alloys (using the internal standardization method) as well as for copper, the major element. The effects of laser pulse duration and energy on laser-induced plasma parameters, namely the excitation temperature and the electron density have been studied in our effort to optimize the analysis. Finally, LIBS analysis was carried on three real metal objects and the spectra obtained have been used to estimate the type and elemental composition of the alloys based on the calibration curves produced with the reference alloys. The results obtained are very useful in the future use of portable LIBS systems for in situ qualitative and quantitative elemental analysis of bronze artifacts in museums and archaeological sites.
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paper_title: Laser-induced breakdown spectroscopy for detection of explosives residues: a review of recent advances, challenges, and future prospects

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In this review we discuss the application of laser-induced breakdown spectroscopy (LIBS) to the problem of detection of residues of explosives. Research in this area presented in open literature is reviewed. Both laboratory and field-tested standoff LIBS instruments have been used to detect explosive materials. Recent advances in instrumentation and data analysis techniques are discussed, including the use of double-pulse LIBS to reduce air entrainment in the analytical plasma and the application of advanced chemometric techniques such as partial least-squares discriminant analysis to discriminate between residues of explosives and non-explosives on various surfaces. A number of challenges associated with detection of explosives residues using LIBS have been identified, along with their possible solutions. Several groups have investigated methods for improving the sensitivity and selectivity of LIBS for detection of explosives, including the use of femtosecond-pulse lasers, supplemental enhancement of the laser-induced plasma emission, and complementary orthogonal techniques. Despite the associated challenges, researchers have demonstrated the tremendous potential of LIBS for real-time detection of explosives residues at standoff distances.
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paper_title: Development of a mobile system based on laser-induced breakdown spectroscopy and dedicated to in situ analysis of polluted soils ☆

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Principal Components Analysis (PCA) is successfully applied to the full laser-induced breakdown spectroscopy (LIBS) spectra of soil samples, defining classes according to the concentrations of the major elements. The large variability of the LIBS data is related to the heterogeneity of the samples and the representativeness of the data is finally discussed. Then, the development of a mobile LIBS system dedicated to the in-situ analysis of soils polluted by heavy metals is described. Based on the use of ten-meter long optical fibers, the mobile system allows deported measurements. Finally, the laser-assisted drying process studied by the use of a customized laser has not been retained to overcome the problem of moisture.
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paper_title: Laser-Induced Breakdown Spectroscopy in open-path configuration for the analysis of distant objects

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A review of recent results on stand-off Laser-Induced Breakdown Spectroscopy (LIBS) analysis and applications is presented. Stand-off LIBS was suggested for elemental analysis of materials located in environments where any physical access was not possible but optical access could be envisaged. This review only refers to the use of the open-path LIBS configuration in which the laser beam and the returning plasma light are transmitted through the atmosphere. It does not present the results obtained with a transportation of the laser pulses to the target through an optical fiber. Open-path stand-off LIBS has mainly been used with nanosecond laser pulses for solid sample analysis at distances of tens of meters. Liquid samples have also been analyzed at distances of a few meters. The distances achievable depend on many parameters including the laser characteristics (pulse energy and power, beam divergence, spatial profile) and the optical system used to focus the pulses at a distance. A large variety of laser focusing systems have been employed for stand-off analysis comprising refracting or reflecting telescope. Efficient collection of the plasma light is also needed to obtain analytically useful signals. For stand-off LIBS analysis, a lens or a mirror is required to increase the solid angle over which the plasma light can be collected. The light collection device can be either at an angle from the laser beam path or collinear with the optical axis of the system used to focus the laser pulses on the target surface. These different configurations have been used depending on the application such as rapid sorting of metal samples, identification of material in nuclear industry, process control and monitoring in metallurgical industry, applications in future planetary missions, detection of environmental contamination or cleaning of objects of cultural heritage. Recent stand-off analyses of metal samples have been reported using femtosecond laser pulses to extend LIBS capabilities to very long distances. The high-power densities achievable with these laser pulses can also induce self-guided filaments in the atmosphere which produce LIBS excitation of a sample. The first results obtained with remote filament-induced breakdown spectroscopy predict sample analysis at kilometer ranges.
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paper_title: Characterization of jewellery products by laser-induced breakdown spectroscopy

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Abstract The suitability of laser-induced breakdown spectroscopy (LIBS) for the characterization of jewellery products is demonstrated by the development of a method based on the use of an Nd-YAG laser (operating at 532 nm) which induces ablation of the material and the production of a plasma whose emission reaches 1/8 m spectrograph (connected to a coupled charge detector (CCD)) through an optic fiber. The treatment of the instrumental signal provides enough analytical information, both for identifying and quantifying the major metals present in this type of material. The method proposed has been developed both by multivariate optimization and calibration procedures with application of the appropriate quality criteria. The chemometric analysis of the data and the use of PLS regression for calibration guarantee the ruggedness of the proposed method. The study of the emission spectra allows characterization of the most common noble metals (gold and silver) as well as other metals present in jewellery pieces.
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paper_title: Single Pulse-Laser Induced Breakdown Spectroscopy in aqueous solution

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In this paper the flexibility of Laser Induced Breakdown Spectroscopy (LIBS) has been proved for the analysis of water solutions. The plasma is generated directly in the bulk of a water solution by a Q-switched Nd:YAG laser (1064). The emission signal of four different solutions has been studied: AlCl3, NaCl, CaCO3 and LiF. The basic mechanisms influencing the emission signal and the experimental tricks for the optimization of the detection mode have been pointed out.
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paper_title: From LASER to LIBS, the path of technology development☆

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Abstract Laser-induced breakdown spectroscopy has made significant progress towards becoming a commercial, deployed technology. Its historical development will be reviewed, using the transformation of the laser into commercial technology as a parallel.
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paper_title: Methodologies for laboratory Laser Induced Breakdown Spectroscopy semi-quantitative and quantitative analysis—A review ☆

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Abstract Since its early applications, Laser Induced Breakdown Spectroscopy has been recognized as a useful tool for solid state chemical analysis. However the quantitative accuracy of the technique depends on the complex processes involved in laser induced plasma formation, ablation, atomization, excitation and ion recombination. Problems arising from laser target coupling, matrix effect, fractionation in target vaporization, local thermodynamic equilibrium assumption and interferences from additional air ionization should be properly addressed in order to obtain reliable quantitative results in laboratory to be used as starting point during field campaigns. As selected case studies carried out within the authors' research team show, a proper selection of laser parameters and, in general of experimental conditions, for laboratory data acquisition is required in order to minimize the mentioned problems both in case of calibration curves and calibration free approaches. In particular, the choice of reference samples for measuring calibration curves is of crucial importance in laboratory experiments, in relation both to matrix effect and local thermodynamic equilibrium, to be carried out at comparable conditions in terms of temperature and electron density. A model for the ablation process aimed to the optimization of experimental conditions in some case studies (copper alloys) has been specifically developed in order to account for the target stoichiometry in the plasma. Problems related to the limit of detection for quantitative trace analysis have been considered in analyzing data collected both inside and outside the local thermodynamic equilibrium window, in cases characterized by a fixed contamination threshold.
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paper_title: Determination of heavy metals in soils by Laser Induced Breakdown Spectroscopy

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Laser Induced Breakdown Spectroscopy (LIBS) is a recent analytical technique that is based upon the measurement of emission lines generated by atomic species close to the surface of the sample, thus allowing their chemical identification. In this work, the LIBS technique has been applied to the determination of total contents of heavy metals in a number of reference soil samples. In order to validate the technique, LIBS data were compared with data obtained on the same soil samples by application of conventional Inductively Coupled Plasma (ICP) spectroscopy. The partial agreement obtained between the two sets of data suggested the potential applicability of the LIBS technique to the measurement of heavy metals in soils.
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paper_title: Accurate quantitative analysis of gold alloys using multi-pulse laser induced breakdown spectroscopy and a correlation-based calibration method

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Abstract Multi-pulse laser induced breakdown spectroscopy (LIBS), in combination with the generalized linear correlation calibration method (GLCM), was applied to the quantitative analysis (fineness determination) of quaternary gold alloys. Accuracy and precision on the order of a few thousandths (‰) was achieved. The analytical performance is directly comparable to that of the standard cupellation method (fire assay), but provides results within minutes and is virtually non-destructive, as it consumes only a few micrograms of the sample.
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paper_title: From single pulse to double pulse ns-Laser Induced Breakdown Spectroscopy under water : Elemental analysis of aqueous solutions and submerged solid samples

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Abstract In this paper the developments of Laser Induced Breakdown Spectroscopy (LIBS) underwater have been reviewed to clear up the basic aspects of this technique as well as the main peculiarities of the analytical approach. The strong limits of Single-Pulse (SP) LIBS are discussed on the basis of plasma emission spectroscopy observations, while the fundamental improvements obtained by means of the Double-Pulse (DP) technique are reported from both the experimental and theoretical point of view in order to give a complete description of DP-LIBS in bulk water and on submerged solid targets. Finally a detailed description of laser–water interaction and laser-induced bubble evolution is reported to point out the effect of the internal conditions (radius, pressure and temperature) of the first pulse induced bubble on the second pulse producing plasma. The optimization of the DP-LIBS emission signal and the determination of the lower detection limit, in a set of experiments reported in the current scientific literature, clearly demonstrate the feasibility and the advantages of this technique for underwater applications.
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paper_title: A compact and portable laser-induced breakdown spectroscopy instrument for single and double pulse applications

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Abstract We present LIBS experimental results that demonstrate the use of a newly developed, compact, versatile pulsed laser source in material analysis related to art and archaeological applications in view of research aiming at the development of portable LIBS instrumentation. LIBS qualitative analysis measurements were performed on various samples and objects, and the spectra were recorded in gated and non-gated modes. The latter is important because of advantages arising from size and cost reduction when using simple, compact spectrograph-CCD detection systems over the standard ICCD-based configurations. The new laser source exhibited a very reliable performance in terms of laser pulse repeatability, autonomy and interface. Having the ability to work in double pulse mode it provided versatility in the measurements leading to increased LIBS signal intensities, improved the signal-to-noise ratio and the RSD of the spectra. The first test results are encouraging and demonstrate that this new laser is suitable for integration in compact, portable LIBS sensors with a wide spectrum of materials analysis applications.
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paper_title: Analysis of heavy metals in soils using laser-induced breakdown spectrometry combined with laser-induced fluorescence

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Abstract The investigation of a hyphenated technique combining laser-induced breakdown spectrometry (LIBS) with laser-induced fluorescence (LIF) for the analysis of heavy metals in soils is described. In order to evaluate the applicability of the technique for fast in-situ analytical purposes, measurements were performed at atmospheric pressure. The plasma radiation was detected using a Paschen–Runge spectrometer equipped with photomultipliers for the simultaneous analysis of 22 different elements. The photomultiplier signals were processed by a fast gateable multichannel integrator. Calibration curves were recorded using a set of spiked soil samples. Limits of detection were derived from these curves for As (3.3 μg/g), Cd (6 μg/g), Cr (2.5 μg/g), Cu (3.3 μg/g), Hg (84 μg/g), Ni (6.8 μg/g), Pb (17 μg/g), Tl (48 μg/g) and Zn (98 μg/g) using the LIBS signals. LIBS-LIF measurements were performed for Cd and Tl. The excitation wavelength as well as the detected fluorescence wavelength for Cd was 228.8 nm. Alternatively, Tl was excited at 276.8 nm, where the observed fluorescence wavelength was 351.9 nm. The calibration curves based on the LIF signals showed significantly improved limits of detection of 0.3 and 0.5 μg/g for Cd and Tl, respectively.
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paper_title: Rank correlation of laser-induced breakdown spectroscopic data for the identification of alloys used in jewelry manufacture

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Abstract The aim of the present study was the rapid identification of alloys used in the manufacture of jewelry pieces with the help of a spectral library. The laser-induced breakdown spectra of 32 alloys were stored, with 25 of them chosen as library standards; the remaining seven spectra were used as samples. The composition of the alloys was obtained by flame atomic absorption spectrometry. A rank correlation method was applied for comparison between spectra, providing good correlation coefficients for the alloys studied. The composition of the samples was also predicted by partial least-squares regression to demonstrate the capability of this technique for the rapid analysis of this type of material.
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paper_title: Laser-induced breakdown spectroscopy applications in the steel industry: Rapid analysis of segregation and decarburization ☆

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Abstract Rapid chemical analysis is increasingly a prerequisite in the steel making industry, either to check that a steel product complies with customers' specifications, or to investigate the presence of defects that may lead to mechanical property failure of the product. Methods conventionally used for assessment, such as the monitoring of decarburization and segregation, performed by chemical etching of a polished surface followed by optical observation, tend to be relatively fast, simple and applicable to large sample areas; however, the information obtained is limited to the spatial extent of the defect. Other techniques, such as electron probe microscopy and scanning electron microscopy — energy dispersive X-ray, can be used for providing detailed chemical composition at the micro-scale, for a better understanding of the mechanisms involved; however, their use is limited to analyzing comparatively very small sample areas (typically a few mm 2 ). The ability to rapidly generate chemical concentration maps at the micro-scale is one of the many positive attributes of laser-induced breakdown spectroscopy (LIBS) that makes it a useful tool for the steel industry as a laboratory or near-the-line analysis facility. Parameters that influence the detailed mapping of large sample areas were determined and optimized. LIBS scanning measurements were performed on samples displaying segregation and decarburization. A 60 × 60 mm 2 area, with a step size of 50 μm, was measured in 35 min on segregation samples, and a 4 × 1 mm 2 area with a step size of 20 μm in 2 min on a decarburization sample. The resulting quantified elemental maps correlated very well with data from the methods used conventionally. In the two examples above, the application of LIBS as a micro-analysis technique proved to bring very valuable information that was not accessible previously with other techniques on such large areas in such a short time.
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paper_title: Laser induced plasma spectroscopy for local equivalence ratio measurements in an oscillating combustion environment

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Abstract Equivalence ratios measured with a laser induced plasma spectroscopy (LIPS, also referred as LIBS) are reported in two different setups. First, a small premixed turbulent burner is used to address fundamental issues concerning the LIPS technique. It is shown that hydrogen excitation within the created plasma is the key parameter to measure in order to retrieve correctly equivalence ratio measurements. Results compared with a spark energy classification strategy show better results with excitation classification, as variations in ratio between the different lines come not only from gaseous concentration but also from plasma’s characteristics. Using spectra from 450 to 800 nm allows the determination of two independent emission ratios to improve single shot accuracy. The developed approach is afterwards applied to phase-locked measurements of equivalence ratio in a lean premixed combustor, for which strong thermo-acoustics oscillations exist. This combustor runs with methane–air, preheated at 700 K and with a typical equivalence ratio of 0.50, for which the sound pressure levels of the oscillations are 170 dB. Measurements at the inlet of the combustor reveal strong correlations between fluctuations of the incoming stoichiometry and pressure fluctuations. It is shown that stoichiometry changes within one oscillating cycle of about 3%. Those changes are crucial for the flame dynamics as dealing with very lean mixtures.
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paper_title: Laser-induced breakdown spectroscopy of bulk aqueous solutions at oceanic pressures: evaluation of key measurement parameters.

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The development of in situ chemical sensors is critical for present-day expeditionary oceanography and the new mode of ocean observing systems that we are entering. New sensors take a significant amount of time to develop; ::: therefore, validation of techniques in the laboratory for use in the ocean environment is necessary. Laser-induced breakdown spectroscopy (LIBS) is a promising in situ technique for oceanography. Laboratory investigations on the feasibility of using LIBS to detect analytes in bulk liquids at oceanic pressures were carried out. LIBS was successfully used to detect dissolved Na, Mn, Ca, K, and Li at pressures up to ::: 2.76×107 Pa. The effects of pressure, laser-pulse energy, interpulse delay, gate delay, temperature, and NaCl concentration on the LIBS signal were examined. An optimal range of laser-pulse energies was found to exist for analyte detection in bulk aqueous solutions at both low and high pressures. No pressure effect was seen on the emission intensity for Ca and Na, and an increase in emission intensity with increased pressure was seen for Mn. Using the dual-pulse technique for several analytes, a very short interpulse delay resulted in the greatest emission intensity. The presence of NaCl enhanced the emission intensity for Ca, but had no effect on peak intensity of Mn or K. Overall, increased pressure, the addition of NaCl to a solution, and temperature did not inhibit detection of analytes in solution and sometimes even enhanced the ability to detect the analytes. The results suggest that LIBS is a viable chemical sensing method for in situ analyte detection in high-pressure environments such as the deep ocean.
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paper_title: Quantitative micro-analysis by laser-induced breakdown spectroscopy: a review of the experimental approaches

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Abstract The laser-induced breakdown spectroscopy (LIBS) technique has shown in recent years its great potential for rapid qualitative analysis of materials. Because of the lack of pre-treatment of the material, as well as the speed of analysis, not mentioning the possibility of in situ analysis, this technique offers an attractive solution for a wide range of industrial applications. As a consequence, a lot of work has been devoted towards the application of LIBS technique for quantitative micro-analysis. The purpose of this paper is to give a review of the current experimental approaches used for obtaining quantitative micro-analysis using the LIBS technique. The influence on LIBS analytical performances of laser power, wavelength and pulse length, the proper choice of experimental geometry, the importance of ambient gas choice and the role of detectors for improving the precision of LIBS analysis are among the topics discussed in this paper.
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paper_title: Chronocultural sorting of archaeological bronze objects using laser-induced breakdown spectrometry

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This work discusses the capability of laser-induced breakdown spectrometry (LIBS) for characterization and cataloging of metallic objects belonging to the Bronze and Iron Ages. A set of 37 metallic objects from different locations of the South East of Iberian Peninsula has been sorted according to their metal content. Arsenic concentration in metallic objects has been found a key factor for distinguishing between Bronze and Iron Ages objects, allowing the chronocultural sorting of each piece. For this study, a pulsed Q-switched Nd:YAG laser was used to generate a microplasma onto the sample surface. To quantify and catalogue these metallic objects, calibration curves for copper, arsenic, tin, lead and iron were established. The quantitative results demonstrate that the chronological sorting carried out by LIBS matches agreeably with archaeological dating criteria.
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paper_title: Use of LIBS for rapid characterization of parchment.

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Parchment from different sources has been analyzed by laser-induced breakdown spectroscopy (LIBS) for determination of Ca, Na, K, Mg, Fe, Cu, and Mn. The LIBS results were compared with results from inductively coupled plasma spectroscopy (ICP) and good correlation was obtained. Rapid distinction between modern and historical samples was achieved by discriminant analysis of the LIBS data. Animal type recognition was also possible on the basis of Mg/Cu emission peak ratio and Mg depth profiling.
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paper_title: Time-resolved characterization of laser-induced plasma from fresh potatoes

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Abstract Optical emission of laser-induced plasma on the surface of fresh vegetables provides sensitive analysis of trace elements for in situ or online detection of these materials. This emergent technique promises applications with expected outcomes in food security or nutrition quality, as well as environment pollution detection. Characterization of the plasma induced on such soft and humid materials represents the first step towards quantitative measurement using this technique. In this paper, we present the experimental setup and protocol that optimize the plasma generation on fresh vegetables, potatoes for instance. The temporal evolution of the plasma properties are investigated using time-resolved laser-induced breakdown spectroscopy (LIBS). In particular, the electron density and the temperatures of the plasma are reported as functions of its decay time. The temperatures are evaluated from the well known Boltzmann and Saha-Boltzmann plot methods. These temperatures are further compared to that of the typical molecular species, CN, for laser-induced plasma from plant materials. This comparison validates the local thermodynamic equilibrium (LTE) in the specific case of fresh vegetables ablated in the typical LIBS conditions. A study of the temporal evolution of the signal to noise ratio also provides practical indications for an optimized detection of trace elements. We demonstrate finally that, under certain conditions, the calibration-free LIBS procedure can be applied to determine the concentrations of trace elements in fresh vegetables.
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paper_title: Sequential-Pulse Laser-Induced Breakdown Spectroscopy of High-Pressure Bulk Aqueous Solutions

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Sequential-pulse (or dual-pulse) laser-induced breakdown spectroscopy (DP-LIBS) with an orthogonal spark orientation is described for elemental analysis of bulk aqueous solutions at pressures up to approximately 138 x 10(5) Pa (138 bar). The use of sequential laser pulses for excitation, when compared to single-pulse LIBS excitation (SP-LIBS), provides significant emission intensity enhancements for a wide range of elements in bulk solution and allows additional elements to be measured using LIBS. Our current investigations of high-pressure solutions reveal that increasing solution pressure leads to a significant decrease in DP-LIBS emission enhancements for all elements examined, such that we see little or no emission enhancements for pressures above 100 bar. Observed pressure effects on DP-LIBS enhancements are thought to result from pressure effects on the laser-induced bubble formed by the first laser pulse. These results provide insight into the feasibility and limitations of DP-LIBS for in situ multi-elemental detection in high-pressure aqueous environments like the deep ocean.
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paper_title: Laser-induced breakdown spectrometry — applications for production control and quality assurance in the steel industry

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Abstract Recent progress in sensitivity and signal processing opened a broad field of application for laser-induced breakdown spectrometry (LIBS) in the steel making and processing industry. Analyzed substances range from top gas of the blast furnace, via liquid steel up to finished products. This paper gives an overview of R&D activities and first routine industrial applications of LIBS. The continuous knowledge of the topgas composition yields information about the blast furnace process. An online monitoring method using LIBS is currently under investigation to measure alkali metals, which influence energy and mass flow in the furnace. Direct analysis of liquid steel reduces processing times in secondary metallurgy. By using sensitivity-enhanced LIBS, limits of detection of approximately 10 μg/g and below were achieved for light and heavy elements in liquid steel. The process control in steel production relies on the results from the chemical analysis of the slag. A prototype of an analytical system was developed using LIBS to analyze slag samples two times faster than with conventional methods. The cleanness of steel is a key issue in the manufacturing of spring steel, thin foils and wires. Microscopic inclusions have to be determined quickly. A scanning microanalysis system based on LIBS was developed with measuring frequencies up to 1 kHz and a spatial resolution of
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paper_title: Particle size limits for quantitative aerosol analysis using laser-induced breakdown spectroscopy: Temporal considerations

paper_content:

Abstract The temporal evolution of the Si atomic emission signal produced from individual silica microspheres in an aerosolized air stream was investigated using laser-induced breakdown spectroscopy (LIBS). Specifically, the temporal evolution of Si emission from 2.47 and 4.09-micrometer-sized particles is evaluated over discrete delay times ranging from 15 to 70 µs following plasma initiation. The analyte signal profile from the microspheres, taken as the silicon atomic emission peak-to-continuum ratio, was observed to follow the same profile of silicon-rich nanoparticles over the range of delay times. The ratio of analyte signals for the 2.47 and 4.09-micrometer particles was observed to be approximately constant with plasma decay time and less than the expected mass ratio, leading to the conclusion that further vaporization and enhanced analyte response do not continue with increasing delay times for these microsphere sizes. While recent research suggests that the temporal component of analyte response is important for quantitative LIBS analysis, the current study does confirm earlier research demonstrating an upper size limit for quantitative aerosol particle analysis in the diameter range of 2 to 2.5 µm for silica microspheres.
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paper_title: Laser-induced breakdown spectroscopy (LIBS) in archaeological science—applications and prospects

paper_content:

Laser-induced breakdown spectroscopy (LIBS) has emerged in the past ten years as a promising technique for analysis and characterization of the composition of a broad variety of objects of cultural heritage including painted artworks, icons, polychromes, pottery, sculpture, and metal, glass, and stone artifacts. This article describes in brief the basic principles and technological aspects of LIBS, and reviews several test cases that demonstrate the applicability and prospects of LIBS in the field of archaeological science.
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paper_title: LIBS-spectroscopy for monitoring and control of the laser cleaning process of stone and medieval glass

paper_content:

Abstract On-line monitoring or even closed-loop control is necessary to avoid over-cleaning in case the ablation process is not self-limiting. Therefore, the laser-induced breakdown spectroscopy (LIBS) was used. Basic investigations were carried out on original sandstone samples ( Elbsandstein ) with strong encrustations as well as medieval stained glass samples (13th century from Cologne Cathedral). The spectroscopic study has shown that the plasma emission can be used for determination of the elemental composition of the ablated material. The plasma was initiated by 248-nm pulses of an KrF-excimer laser (30 ns FWHM). For the spectroscopic analysis, a grating spectrograph in combination with an optical multichannel analyser was used. For the glass and stone samples we obtained a continual alteration of the LIBS spectrum (vanishing of peaks and generating of new element peaks) during the removal process. Thus, certain element peaks can be used to distinguish between encrustation layer and valuable underlying material. To show the potential of LIBS we designed an experimental laser cleaning set-up including closed-loop LIBS control and demonstrated successful automatic cleaning of an original glass fragment.
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paper_title: Dual-pulse Laser Induced Breakdown Spectroscopy for analysis of gaseous and aerosol systems: Plasma-analyte interactions

paper_content:

Abstract Dual-pulse LIBS has been previously investigated to a large extent on solid and liquid phase analytes, where it has been demonstrated to significantly enhance atomic emission signal intensity, and more importantly, to enhance the analyte peak-to-base and signal-to-noise ratios. This study focuses on the effects of an orthogonal dual-pulse laser configuration on the atomic emission response for both purely gaseous and calcium-based aerosol samples. The gaseous sample consisted of purified (i.e. aerosol free) air, from which nitrogen and oxygen spectral emission lines were analyzed. Measurements for the gaseous system resulted in no notable improvements with the dual-pulse configuration as compared to the single-pulse LIBS. Experiments were also conducted in purified air seeded with calcium-rich particles, which revealed a marked improvement in calcium atomic emission peak-to-base (∼ 2-fold increase) and signal-to-noise ratios (∼ 4-fold increase) with the dual-pulse configuration. In addition to increased analyte response, dual-pulse LIBS yielded an enhanced single-particle sampling rate when compared to conventional LIBS. Transmission measurements with respect to the plasma-creating laser pulse were recorded for both single and dual-pulse methods over a range of temporal delays. In consideration of the spectroscopic and transmission data, the plasma-analyte interactions realized with a dual-pulse methodology are explained in terms of the interaction with the initially expanding plasma shock wave, which differs between gaseous and particulate phase analytes, as reported in a recent study [V. Hohreiter, D.W. Hahn, Calibration effects for laser-induced breakdown spectroscopy of gaseous sample streams: analyte response of gas-phase species versus solid-phase species, Anal. Chem. 77 (2005) 1118–1124].
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paper_title: Feasibility of generating a useful laser-induced breakdown spectroscopy plasma on rocks at high pressure: preliminary study for a Venus mission

paper_content:

Abstract Laser-induced breakdown spectroscopy (LIBS) is being developed for future use on landers and rovers to Mars. The method also has potential for use on probes to other planets, the Moon, asteroids and comets. Like Mars, Venus is of strong interest because of its proximity to earth, but unlike Mars, conditions at the surface are far more hostile with temperatures in excess of 700 K and pressures on the order of 9.1 MPa (90 atm). These conditions present a significant challenge to spacecraft design and demand that rapid methods of chemical data gathering be implemented. The advantages of LIBS (e.g. stand-off and very rapid analysis) make the method particularly attractive for Venus exploration because of the expected short operational lifetimes (≈2 h) of surface instrumentation. Although the high temperature of Venus should pose no problem to the analytical capabilities of the LIBS spark, the demonstrated strong dependence of laser plasma characteristics on ambient gas pressures below earth atmospheric pressure requires that LIBS measurements be evaluated at the high Venus surface pressures. Here, we present a preliminary investigation of LIBS at 9.1 MPa for application to the analysis of a basalt rock sample. The results suggest the feasibility of the method for a Venus surface probe and that further study is justified.
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paper_title: ns- and fs-LIBS of copper-based-alloys: A different approach

paper_content:

A self-calibrated analytical technique, based on plasmas induced by either 250 fs or 7 ns laser pulses, is presented. This approach is comparable to other calibration-free methods based on LTE assumption. In order to apply this method to very different laser pulse durations, the partial-local thermodynamic equilibrium (p-LTE) has been considered within the energy range of 30,000-50,000 cm -1 . In order to obtain the neutral species densities, the detected plasma species emission lines intensities have been treated together with the experimental evaluated background black-body Planck-like emission distribution. For validating the followed method, three certified copper-based-alloys standards were employed and their minor components (Ni, Pb and Sn) amounts were determined. As a result, it arises, that this standardless method, independently from the laser source pulse durations, provides good quantitative analysis, and, consequently, that the composition of the plasma plume emitting species induced is not affected by the laser pulse time width.
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paper_title: Laser Induced Breakdown Spectroscopy methodology for the analysis of copper-based-alloys used in ancient artworks☆

paper_content:

Abstract In this paper Laser Induced Breakdown Spectroscopy has been applied for determining the elemental composition of a set of ancient bronze artworks coming from archaeological site of Minervino Murge — Southern of Italy (dated around VII b.C.). Before carrying on the analysis of the archaeological samples, the characterization of the analytical technique has been accomplished by investigating the trueness of the typical assumptions adopted in LIBS, such as Local Thermodynamic Equilibrium, congruent ablation and plasma homogeneity. With this purpose, two different laser pulse durations, 7 ns and 350 fs, have been used. We have focused our attention on LIBS analysis of bronze standards by considering and discussing the bases of both methodology and analytical approach to be followed for the analysis of ancient copper-based-alloy samples. Unexpectedly, regardless from the laser pulse duration, the LIBS technique has shown, by considering an adequate approach on the emitting plasma features, that its peculiarities are anyway preserved so that a fast analysis of ancient copper-based-alloys can be achieved. After verifying the suitability of the methodology, it has been possible to fulfill the typical assumptions considered for the LIBS calibration curves method and use it for ancient bronze artworks analysis.
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paper_title: On board LIBS analysis of marine sediments collected during the XVI Italian campaign in Antarctica

paper_content:

Abstract The Laser-induced Breakdown Spectroscopy technique was applied on board the R/V Italica during the XVI Antarctic campaign (2000–2001) to carry out elemental chemical analysis of marine sediments collected using different sampling systems. To this end, a compact system has been built, which was suitable to operate also in the presence of mechanical vibrations, induced by the ship motion. Qualitative and quantitative analyses were performed on dried samples, without any further pre-treatment. Qualitative analyses have shown similar elemental composition among different collected sediments, except for significant differences in the case of rock fragments and manganese nodule. The latter also contains some heavy metals that in sediment layers were detected only in traces. The methodology to retrieve relative or absolute elemental concentration in heterogenous samples has been optimized and is scarcely sensitive to variations of sediment physical properties with depth, and to experimental parameters such as laser defocusing because of surface irregularities, and laser energy fluctuations. The relative distribution of the major elemental constituents, both from a bio-organic and mineral origin, was measured as a function of sediment depth. Measurements, once limited to specific spectral sections, and data analyses are fast and very reproducible. Most of the elements show a gradually varying distribution along the sampled core, except for silicon and barium, whose steep decrease with depth is strongly related to their biogenic origin. Quantitative LIBS analyses were performed on a limited number of samples and the results reported here, are comparable to the certified element contents in a reference sample of Antarctic sediments.
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paper_title: Effect of Pulse Delay Time on a Pre-Ablation Dual-Pulse LIBS Plasma

paper_content:

In this paper, we investigate the effect of dual-pulse timing on material ablation, plasma temperature, and plasma size for pre-ablation spark dual-pulse laser-induced breakdown spectroscopy (LIBS). Although the plasma temperature increases for dual-pulse excitation, the signal enhancement is most easily attributed to increased sample ablation. Plasma images show that the magnitude of the enhancement can be affected by the collection optic and by the collection geometry. Enhancements calculated using the total integrated intensity of the plasma are comparable to those measured using fiber-optic collection.
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paper_title: Nanosecond and femtosecond Laser Induced Breakdown Spectroscopic analysis of bronze alloys

paper_content:

Abstract In the present work we are studying the influence of pulse duration (nanosecond (ns) and femtosecond (fs)) at λ = 248 nm on the laser-induced plasma parameters and the quantitative analysis results for elements such as Sn, Zn and Pb, in different types of bronze alloys adopting LIBS in ambient atmosphere. Binary (Sn–Cu), ternary (Sn–Zn–Cu or Sn–Pb–Cu) and quaternary (Sn–Zn–Pb–Cu) reference alloys characterized by a chemical composition and metallurgical features similar to those used in Roman times, were employed in the study. Calibration curves, featuring linear regression coefficients over 98%, were obtained for tin, lead and zinc, the minor elements in the bronze alloys (using the internal standardization method) as well as for copper, the major element. The effects of laser pulse duration and energy on laser-induced plasma parameters, namely the excitation temperature and the electron density have been studied in our effort to optimize the analysis. Finally, LIBS analysis was carried on three real metal objects and the spectra obtained have been used to estimate the type and elemental composition of the alloys based on the calibration curves produced with the reference alloys. The results obtained are very useful in the future use of portable LIBS systems for in situ qualitative and quantitative elemental analysis of bronze artifacts in museums and archaeological sites.
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paper_title: Excitation equilibria in plasmas; a classification

paper_content:

The rich nature of the plasma state manifests itself in the large variety of studies focused on the atomic state distribution function (ASDF). Many specific calculations dedicated to various exemplary plasma situations can be found in literature. In this study we follow and continue the line of Bibermanl, Fujimoto2, and Seaton3 by trying to find a classification in these results4. The central item is to find a (analytical) relation between the ASDF and the underlying plasma properties. We confine ourselves to those situations in which the excitation kinetics is ruled by (Maxwellian) electrons in atomic plasmas. Molecular processes will not be considered.
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paper_title: From single pulse to double pulse ns-Laser Induced Breakdown Spectroscopy under water : Elemental analysis of aqueous solutions and submerged solid samples

paper_content:

Abstract In this paper the developments of Laser Induced Breakdown Spectroscopy (LIBS) underwater have been reviewed to clear up the basic aspects of this technique as well as the main peculiarities of the analytical approach. The strong limits of Single-Pulse (SP) LIBS are discussed on the basis of plasma emission spectroscopy observations, while the fundamental improvements obtained by means of the Double-Pulse (DP) technique are reported from both the experimental and theoretical point of view in order to give a complete description of DP-LIBS in bulk water and on submerged solid targets. Finally a detailed description of laser–water interaction and laser-induced bubble evolution is reported to point out the effect of the internal conditions (radius, pressure and temperature) of the first pulse induced bubble on the second pulse producing plasma. The optimization of the DP-LIBS emission signal and the determination of the lower detection limit, in a set of experiments reported in the current scientific literature, clearly demonstrate the feasibility and the advantages of this technique for underwater applications.
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paper_title: Experimental characterization of metallic titanium-laser induced plasma by time and space resolved optical emission spectroscopy

paper_content:

Abstract Time and space resolved optical emission spectroscopy has been successfully employed to investigate the evolution of the plasma produced by the interaction of UV laser beam with a metallic target of titanium at two different pressures (10 −5 and 3.4×10 −2 torr) and at distances up to 3 mm from the target. By time of flight measurements and Boltzmann plots both the dynamic and the kinetic aspects have been discussed. The quasi-equilibrium state of the laser-induced plasma has been established on the basis of the failure of Saha balance equation. The effect of three-body recombination on atomic titanium temporal distribution has been explained. Temporal evolution of electron number density, as determined by Stark effect, has been used for the estimation of the three-body recombination rate constant.
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paper_title: Excitation equilibria in plasmas; a classification

paper_content:

The rich nature of the plasma state manifests itself in the large variety of studies focused on the atomic state distribution function (ASDF). Many specific calculations dedicated to various exemplary plasma situations can be found in literature. In this study we follow and continue the line of Bibermanl, Fujimoto2, and Seaton3 by trying to find a classification in these results4. The central item is to find a (analytical) relation between the ASDF and the underlying plasma properties. We confine ourselves to those situations in which the excitation kinetics is ruled by (Maxwellian) electrons in atomic plasmas. Molecular processes will not be considered.
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paper_title: Theoretical Modeling of Laser Ablation of Quaternary Bronze Alloys: Case Studies Comparing Femtosecond and Nanosecond LIBS Experimental Data†

paper_content:

A model, formerly proposed and utilized to understand the formation of laser induced breakdown spectroscopy (LIBS) plasma upon irradiation with nanosecond laser pulses at different fluences and wavelengths, has been extended to the irradiation with femtosecond laser pulses in order to control the fractionation mechanisms which heavily affect the application of laser-ablation-based microanalytical techniques. The model takes into account the different chemico-physical processes occurring during the interaction of an ultrashort laser pulse with a metallic surface. In particular, a two-temperature description, relevant to the electrons and lattice of the substrate, respectively, has been introduced and applied to different ternary and quaternary copper-based alloys subjected to fs and ns ablation both in the visible (527 nm) and in the UV (248 nm). The model has been found able to reproduce the shorter plasma duration experimentally found upon fs laser ablation. Kinetic decay times of several copper (major e...
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paper_title: From LASER to LIBS, the path of technology development☆

paper_content:

Abstract Laser-induced breakdown spectroscopy has made significant progress towards becoming a commercial, deployed technology. Its historical development will be reviewed, using the transformation of the laser into commercial technology as a parallel.
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paper_title: Characterization of laser induced plasmas by optical emission spectroscopy: A review of experiments and methods

paper_content:

Advances in characterization of laser induced plasmas by optical emission spectroscopy are reviewed in this article. The review is focused on the progress achieved in the determination of the physical parameters characteristic of the plasma, such as electron density, temperature and densities of atoms and ions. The experimental issues important for characterization by optical emission spectroscopy, as well as the different measurement methods are discussed. The main assumptions of the methods, namely the optical thin emission of spectral lines and the existence of local thermodynamic equilibrium in the plasma are evaluated. For dense and inhomogeneous sources of radiation such as laser induced plasmas, the characterization methods are classified in terms of the optical depth and the spatial resolution of the emission used for the measurements. The review deals firstly with optically thin spatially integrated measurements. Next, local measurements and characterization in not optically thin conditions are discussed. Two tables are included that provide reference to the works reporting measurements of electron density and temperature of laser induced plasmas generated with diverse samples.
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paper_title: Calibration-Free Laser-Induced Breakdown Spectroscopy: State of the art

paper_content:

The aim of this paper is offering a critical review of Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS), the approach of multi-elemental quantitative analysis of LIBS spectra, based on the measurement of line intensities and plasma properties (plasma electron density and temperature) and on the assumption of a Boltzmann population of excited levels, which does not require the use of calibration curves or matrix-matched standards. The first part of this review focuses on the applications of the CF-LIBS method. Quantitative results reported in the literature, obtained in the analysis of various materials and in a wide range of experimental conditions, are summarized, with a special emphasis on the departure from nominal composition values. The second part is a discussion of the simplifying assumptions which lie at the basis of the CF-LIBS algorithm (stoichiometric ablation and complete atomization, thermal equilibrium, homogeneous plasma, thin radiation, detection of all elements). The inspection of the literature suggests that the CF-LIBS method is more accurate in analyzing metallic alloys rather than dielectrics. However, the full exploitation of the method seems to be still far to come, especially for the lack of a complete characterization of the effects of experimental constraints. However, some general directions can be suggested to help the analyst in designing LIBS measurements in a way which is more suited for CF-LIBS analysis.
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paper_title: Particle size distributions and compositions of aerosols produced by near-IR femto- and nanosecond laser ablation of brass

paper_content:

Particle size distributions and compositions of primary aerosols produced by means of near-IR femtosecond laser ablation (λ ::: = 775 nm) of brass in He or Ar at atmospheric pressure have been measured. Aerosols were characterized using a 13-stage low-pressure impactor covering a size range from 5 nm up to 5 μm and subsequently analyzed applying total reflection X-ray fluorescence spectrometry. The results indicate, that for femtosecond laser ablation in the low-fluence regime (<5 J cm−2) ultra-fine aerosols (mean diameter dp ::: ≈ 10 nm/peak width wp ::: ≈ 35 nm) are produced. Furthermore, the total Cu/Zn ratio of these aerosols corresponds to the composition of the bulk material. In contrast, ablation above 10 J cm−2 results in the formation of polydisperse, bimodal aerosols, which are distributed around dp1 ::: ≈ 20 nm (wp1 ::: ≈ 50 nm) and dp2 ::: ≈ 1 μm (wp2 ::: ≈ 5 µm), respectively, and whose total Cu/Zn ratio slightly deviates from the bulk composition. In order to examine the influence of pulse duration on particle size distribution and aerosol composition, comparative measurements by means of near-IR nanosecond ablation were also performed. The data show that nanosecond ablation generally leads to an intensified formation of particles in the micrometer range. Moreover, the composition of these aerosols strongly departs from the stoichiometry of the bulk. Aspects concerning the formation of particles during ablation as well as implications for the element-selective analysis by inductively coupled plasma spectrometry are discussed.
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paper_title: Non-equilibrium and equilibrium problems in laser-induced plasmas

paper_content:

Several problems which can determine non-equilibrium effects in laser-induced breakdown plasmas are analysed in this study. In particular, we focus our attention on problems associated with the fluid dynamics of the expanding plume, with time-dependent collisional-radiative models for describing the population densities of excited states, with the time-dependent Boltzmann equation for characterizing the electron energy distribution function in laser-induced breakdown spectroscopy (LIBS) plasmas. The results show that these problems should be carefully taken into account for developing a calibration-free LIBS methodology. Finally, problems associated with equilibrium plasmas, and in particular the dependence of the partition function on the particular environment surrounding the different components of a plasma are discussed.
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paper_title: Correction of self-absorption spectral line and ratios of transition probabilities for homogeneous and LTE plasma

paper_content:

Abstract Expressions for fundamental spectral line parameters are reported for Gaussian and Lorentzian shape profiles for homogeneous plasma at equilibrium in presence of the self-absorption. These expressions for Lorentzian profiles are applied to the determination of the ratios of transition probabilities and the ratios of optical thicknesses by a new method that we propose in this article. The self-absorption is computed by spectral line profiles with a Simplex algorithm program fitting. Applications to some experimental lines illustrate the appropriate corrections.
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paper_title: On the usefulness of a duplicating mirror to evaluate self-absorption effects in laser induced breakdown spectroscopy

paper_content:

Abstract This paper illustrates the application of the well-known approach of duplicating the emission from a plasma by placing a spherical mirror behind it in order to characterize the degree of self-absorption of atomic transitions. It is shown that this simple expedient provides a quick check for the existence of optically thick plasma conditions, and allows one to follow the temporal evolution of the plasma optical depth from the early decay of the continuum emission to the end of the plasma lifetime. The method is applied to a plasma induced at atmospheric pressure by focusing an Nd:YAG laser on different Al-alloy targets. Moreover, if the resolution of the monochromator allows one to obtain the true physical profiles of the lines investigated, a self-absorption correction factor can be calculated, following a methodology described in the plasma diagnostic literature. It is shown that this correction can be used to improve the linearity of calibration curves and to identify outliers in the Saha–Boltzmann plot for temperature evaluation. The data obtained are still the result of line-of-sight measurements, and therefore can only be interpreted in terms of some space-averaged values of the parameters evaluated. Despite this limitation, it is argued that the simple addition of a mirror to a laser induced plasma emission experiment has many advantageous features and should find a more widespread use when performing laser induced breakdown spectroscopy experiments.
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paper_title: A comparison of nanosecond and femtosecond laser-induced plasma spectroscopy of brass samples

paper_content:

The ablation of brass samples in argon shield gas by 170 fs and 6 ns laser pulses has been studied by optical emission spectroscopy of the evolving plasmas. Differences observed in the temporal behavior of the spectral line intensities are explained by the shielding effect of the Ar plasma for ns-pulses and the free expansion of the plasma of the ablated material in case of fs-pulses. Brass with different ZnrCu ratios were used as samples. Different types of crater formation mechanisms in the case of ns- and fs-pulses were observed. At 40 mbar argon pressure the thresholds of ablation were found to be ; 0.1 and ; 1.5 J cm y2 for fs- and ns-pulses, respectively. With an internal standardization of zinc to copper it is possible to correct for differences in the ablation rates and to obtain linear calibration curves. For optimum experimental conditions, narrower confidence intervals for the determination of unknown concentrations were found in case of fs-pulses. Within the range of the laser intensities used, no dependence of the ZnrCu line intensity ratio on the number of laser pulses applied to the same ablation spot was observed, neither for fs- nor for ns-pulses, which is interpreted as the absence of fractional vaporization. Q 2000 Elsevier Science B.V. All rights reserved.
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paper_title: A procedure for correcting self-absorption in calibration free-laser induced breakdown spectroscopy

paper_content:

Abstract A model of the self-absorption effect in laser-induced plasma has been developed, with the aim of providing a tool for its automatic correction in the Calibration-Free algorithm recently developed for standardless analysis of materials by LIBS (Laser Induced Breakdown Spectroscopy). As a test of the model, the algorithm for self-absorption correction is applied to three different certified steel NIST samples and to three ternary alloys (Au, Ag, Cu) of known composition. The experimental results show that the self-absorption corrected Calibration-Free method gives reliable results, improving the precision and the accuracy of the CF-LIBS procedure by approximately one order of magnitude.
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paper_title: Effects of crater development on fractionation and signal intensity during laser ablation inductively coupled plasma mass spectrometry

paper_content:

Abstract The effects of crater development on ICP-MS signal intensities and elemental fractionation have been presented in this work. Craters formed after repetitive 266-nm Nd/YAG laser ablation with 1.0-mJ pulses had a cone-like shape. The laser ablation rate (ng/s) depended on the laser irradiance (laser pulse energy per unit time and unit area), decreasing as irradiance increased. In contrast, the particle entrainment/transport efficiency did not significantly change with irradiance. As the crater-aspect ratio (depth/diameter) increased above some threshold value of six, the Pb/U elemental ratio departed from the stoichiometric value. However, good stoichiometry of ablated mass could be achieved when experimental conditions were carefully selected. The exact mechanism of how crater development affects fractionation is not well understood. In this work, actual irradiance was introduced instead of a nominal value. Actual irradiance decreased as the crater deepened due to changes of the effective area, sampled by the laser beam.
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paper_title: New Procedure for Quantitative Elemental Analysis by Laser-Induced Plasma Spectroscopy

paper_content:

A new procedure, based on the laser-induced plasma spectroscopy (LIPS) technique, is proposed for calibration-free quantitative elemental analysis of materials. The method here presented, based on an algorithm developed and patented by IFAM-CNR, allows the matrix effects to be overcome, yielding precise and accurate quantitative results on elemental composition of materials without use of calibration curves. Some applications of the method are illustrated, for quantitative analysis of the composition of metallic alloys and quantitative determination of the composition of the atmosphere.
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paper_title: A numerical study of expected accuracy and precision in Calibration-Free Laser-Induced Breakdown Spectroscopy in the assumption of ideal analytical plasma ☆

paper_content:

Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS) has been proposed several years ago as an approach for quantitative analysis of Laser-Induced Breakdown Spectroscopy spectra. Recently developed refinement of the spectral processing method is described in the present work. Accurate quantitative results have been demonstrated for several metallic alloys. However, the degree of accuracy that can be achieved with Calibration-Free Laser-Induced Breakdown Spectroscopy analysis of generic samples still needs to be thoroughly investigated. The authors have undertaken a systematic study of errors and biasing factors affecting the calculation in the Calibration-Free Laser-Induced Breakdown Spectroscopy spectra processing. These factors may be classified in three main groups: 1) experimental aberrations (intensity fluctuations and inaccuracy in the correction for spectral efficiency of a detection system), 2) inaccuracy in theoretical parameters used for calculations (Stark broadening coefficients and partition functions) and 3) plasma non-ideality (departure from thermal equilibrium, spatial and temporal inhomogeneities, optical thickness, etc.). In this study, the effects of experimental aberrations and accuracy of spectral data were investigated, assuming that the analytical plasma is ideal. Departure of the plasma conditions from ideality will be the object of future work. The current study was based on numerical simulation. Two kinds of metallic alloys, iron-based and aluminum-based, were studied. The relative weight of the error contributions was found to depend on the sample composition. For the here-investigated samples, the experimental aberrations contribute to the overall uncertainty on the quantitative results more than theoretical parameters. The described simulation method can be applied to the Calibration-Free Laser-Induced Breakdown Spectroscopy analysis of any other kind of sample.
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paper_title: Partial least squares regression for problem solving in precious metal analysis by laser induced breakdown spectrometry

paper_content:

The application of laser induced breakdown spectrometry for the quantitative determination of gold and silver in Au–Ag–Cu alloys is proposed. Laser induced plasma emission spectra in the ultraviolet region were studied in order to characterize the spectral information from time-integrated data. The multivariate calibration method known as partial least squares regression type 1 was used for calibration and prediction purposes. Satisfactory results were obtained for the determination of gold and silver without temporal resolution strategies. Since the employment of this chemometric algorithm was a good alternative for simplification of the experimental setup, a rapid, simple and low cost method is thus proposed for the determination of noble metals in jewelry pieces.
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paper_title: Laser-induced breakdown spectroscopy of composite samples: comparison of advanced chemometrics methods.

paper_content:

Laser-induced breakdown spectroscopy is used to measure chromium concentration in soil samples. A comparison is carried out between the calibration curve method and two chemometrics techniques: partial least-squares regression and neural networks. The three quantitative techniques are evaluated in terms of prediction accuracy, prediction precision, and limit of detection. The influence of several parameters specific to each method is studied in detail, as well as the effect of different pretreatments of the spectra. Neural networks are shown to correctly model nonlinear effects due to self-absorption in the plasma and to provide the best results. Subsequently, principal components analysis is used for classifying spectra from two different soils. Then simultaneous prediction of chromium concentration in the two matrixes is successfully performed through partial least-squares regression and neural networks.
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paper_title: Development of a mobile system based on laser-induced breakdown spectroscopy and dedicated to in situ analysis of polluted soils ☆

paper_content:

Principal Components Analysis (PCA) is successfully applied to the full laser-induced breakdown spectroscopy (LIBS) spectra of soil samples, defining classes according to the concentrations of the major elements. The large variability of the LIBS data is related to the heterogeneity of the samples and the representativeness of the data is finally discussed. Then, the development of a mobile LIBS system dedicated to the in-situ analysis of soils polluted by heavy metals is described. Based on the use of ten-meter long optical fibers, the mobile system allows deported measurements. Finally, the laser-assisted drying process studied by the use of a customized laser has not been retained to overcome the problem of moisture.
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paper_title: Calibration-Free Laser-Induced Breakdown Spectroscopy: State of the art

paper_content:

The aim of this paper is offering a critical review of Calibration-Free Laser-Induced Breakdown Spectroscopy (CF-LIBS), the approach of multi-elemental quantitative analysis of LIBS spectra, based on the measurement of line intensities and plasma properties (plasma electron density and temperature) and on the assumption of a Boltzmann population of excited levels, which does not require the use of calibration curves or matrix-matched standards. The first part of this review focuses on the applications of the CF-LIBS method. Quantitative results reported in the literature, obtained in the analysis of various materials and in a wide range of experimental conditions, are summarized, with a special emphasis on the departure from nominal composition values. The second part is a discussion of the simplifying assumptions which lie at the basis of the CF-LIBS algorithm (stoichiometric ablation and complete atomization, thermal equilibrium, homogeneous plasma, thin radiation, detection of all elements). The inspection of the literature suggests that the CF-LIBS method is more accurate in analyzing metallic alloys rather than dielectrics. However, the full exploitation of the method seems to be still far to come, especially for the lack of a complete characterization of the effects of experimental constraints. However, some general directions can be suggested to help the analyst in designing LIBS measurements in a way which is more suited for CF-LIBS analysis.
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paper_title: Multivariate calibration of spectra obtained by Laser Induced Breakdown Spectroscopy of plutonium oxide surrogate residues

paper_content:

Laser Induced Breakdown Spectroscopy (LIBS) was used to determine elemental concentration of plutonium oxide surrogate (cerium oxide) residue for monitoring the fabrication of lanthanide borosilicate glass. Quantitative analysis by LIBS is affected by the severe limitation of variation in the induced plasma due to changes in the matrix. Multivariate calibration was applied to LIBS data to predict the concentrations of Ce, Cr, Fe, Mo, and Ni. A total of 18 different samples were prepared to compare calibration from univariate data analysis and from multivariate data analysis. Multivariate calibration was obtained using Principal Component Regression (PCR) and Partial Least Squares (PLS). Univariate calibration was obtained from background-corrected atomic emission lines. Calibration results show improvement in the coefficient of determination from 0.87 to 0.97 for Ce compared to univariate calibration. The root mean square error also reduced from 7.46 to 2.93%. A similar trend was obtained for Cr, Fe, Mo, and Ni also. These results clearly demonstrate the feasibility of using LIBS for online process monitoring in a hazardous waste management environment.
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paper_title: Investigation of statistics strategies for improving the discriminating power of laser-induced breakdown spectroscopy for chemical and biological warfare agent simulants

paper_content:

Abstract Laser-induced breakdown spectroscopy spectra of bacterial spores, molds, pollens and nerve agent simulants have been acquired. The performance of several statistical methodologies–linear correlation, principal components analysis, and soft independent model of class analogy–has been evaluated for their ability to differentiate between the various samples. The effect of data selection (total spectra, peak intensities, and intensity ratios) and pre-treatments (e.g., averaging) on the statistical models have also been studied. Results indicate the use of spectral averaging and weighting schemes may be used to significantly improve sample differentiation.
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paper_title: Quantitative micro-analysis by laser-induced breakdown spectroscopy: a review of the experimental approaches

paper_content:

Abstract The laser-induced breakdown spectroscopy (LIBS) technique has shown in recent years its great potential for rapid qualitative analysis of materials. Because of the lack of pre-treatment of the material, as well as the speed of analysis, not mentioning the possibility of in situ analysis, this technique offers an attractive solution for a wide range of industrial applications. As a consequence, a lot of work has been devoted towards the application of LIBS technique for quantitative micro-analysis. The purpose of this paper is to give a review of the current experimental approaches used for obtaining quantitative micro-analysis using the LIBS technique. The influence on LIBS analytical performances of laser power, wavelength and pulse length, the proper choice of experimental geometry, the importance of ambient gas choice and the role of detectors for improving the precision of LIBS analysis are among the topics discussed in this paper.
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paper_title: Nd:YAG laser double wavelength ablation of pollution encrustation on marble and bonding glues on duplicated painting canvas

paper_content:

Abstract In the present study, a newly developed one-beam IR–UV laser cleaning system is presented. This system may be used for different applications in diverse fields, such as outdoors stonework conservation and canvas paintings restoration. The simultaneous use of the fundamental radiation of a Q-switched Nd:YAG laser at 1064 nm and its third harmonic at 355 nm was found appropriate to clean pollution crusts, while ensuring that no discoloration (“yellowing”) would occur. The optimum ratio of UV to IR wavelengths in the final cleaning beam was investigated. In parallel, the same system was tested in diverse applications, such as the removal of bonding glues from duplicated canvases. The optimum laser parameters were investigated both on technical samples as well as on original paintings.
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paper_title: Identification of inks and structural characterization of contemporary artistic prints by laser-induced breakdown spectroscopy

paper_content:

Identification of the inks used in artistic prints and the order in which different ink layers have been applied on a paper substrate are important factors to complement the classical stylistic aspects for the authentication of this type of objects. Laser-induced breakdown spectroscopy (LIBS) is investigated to determine the chemical composition and structural distribution of the constituent materials of model prints made by applying one or two layers of several blue and black inks on an Arches paper substrate. By using suitable laser excitation conditions, identification of the inks was possible by virtue of emissions from key elements present in their composition. Analysis of successive spectra on the same spot allowed the identification of the order in which the inks were applied on the paper. The results show the potential of laser-induced breakdown spectroscopy for the chemical and structural characterization of artistic prints.
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paper_title: Nanosecond-to-femtosecond laser-induced breakdown in dielectrics

paper_content:

We report extensive laser-induced damage threshold measurements on dielectric materials at wavelengths of 1053 and 526 nm for pulse durations {tau} ranging from 140 fs to 1 ns. Qualitative differences in the morphology of damage and a departure from the diffusion-dominated {tau}{sup 1/2} scaling of the damage fluence indicate that damage occurs from ablation for {tau}{le}10 ps and from conventional melting, boiling, and fracture for {tau}{approx_gt}50 ps. We find a decreasing threshold fluence associated with a gradual transition from the long-pulse, thermally dominated regime to an ablative regime dominated by collisional and multiphoton ionization, and plasma formation. A theoretical model based on electron production via multiphoton ionization, Joule heating, and collisional (avalanche) ionization is in quantitative agreement with the experimental results.
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paper_title: Morphology and mechanisms of formation of natural patinas on archaeological Cu-Sn alloys

paper_content:

Abstract Natural patinas on archaeological bronzes (Cu–Sn alloys) have been classified and characterized in order to get a deeper insight into their formation mechanisms. From examinations of cross-sections on archaeological artefacts, two classes of corrosion structures were defined (Type I and Type II), using both optical and electron microscopies, EDSX, XRD, IRS and a statistical treatment of data (Principal Components Analysis). A Type I structure (even surface) is defined as a two-layer passivating deposit due to an internal oxidation with a decuprification process (i.e. selective dissolution of copper). A Type II structure (coarse surface) corresponds to more severe attacks, such as pitting but also general uneven corrosion; it is modelled by a three-layer structure, characterized by the presence of cuprous oxide and by an increase in the chloride content at the internal layer/alloy interface related with selective dissolution of copper. A phenomenological model to explain the formation of bronze patinas is developed on the basis of a decuprification phenomenon.
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paper_title: Experimental investigations of stained paper documents cleaned by the Nd:YAG laser pulses

paper_content:

Abstract The historical paper samples from XIII–XIX c. are characterised by means of techniques of the optical spectroscopy. The influence of pulsed laser cleaning by means of the Q-switched Nd:YAG laser at 532 nm on the spectra and also cleaning results of stained paper documents are reported and considered. In the absorption spectra, the minima around 280 and 370 nm are identified and luminescence reveals a characteristic band centred around 430 nm. The laser cleaning diagnosed by the recording of the LIF spectra with 266 nm excitation shows a profile of increasing intensity and preserved structure. The LIPS spectra reveal sharp emission lines recorded at 612.5, 644.2, 646.5, 671, 714.9, 720.2 nm (Ca I), 589.4, 616.4, 780 nm (Na I), and 766.5: 769.9 nm (Mg I) which are ascribed to the surface contaminations. The intensity decrease of these peaks is in accordance with successive laser pulses and monitors the cleaning progress of the stained paper.
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paper_title: Double-pulse LIBS in bulk water and on submerged bronze samples

paper_content:

In this work laser-induced breakdown spectroscopy (LIBS) has been applied in bulk water using a double-pulse laser source. As in the case of former experiments in air, the use of the double-pulse technique allows for enhancing line emission intensity and reducing the duration of the continuum spectrum, thus increasing the overall analytical performances of the technique. Tap water analysis of Na and Mg dissolved cations has been performed to investigate the capability of the technique, but most significant results have been obtained in determining the composition of submerged bronze targets by laser ablation of their surface in seawater. When the plasma is generated by double-pulse laser, the ablated matter is strongly confined by the water vapor inside the cavitations bubble. The confinement of the plasma leads to higher values of excitation temperature and holds the conditions suitable for chemical analysis (homogeneity and LTE) longer than what happens in gaseous media. The double-pulse experiments performed directly in bulk water point out the features of LIBS technique for real analytical applications in situ, such as the water quality assessment and the investigation of irremovable submerged objects.
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paper_title: The potential of laser-induced breakdown spectrometry for real time monitoring the laser cleaning of archaeometallurgical objects☆

paper_content:

In this work, an orthogonal double pulse (DP) laser-induced breakdown spectroscopy configuration as a diagnostic tool for the restoration of archaeometallurgical samples has been developed and evaluated. Although laser-induced breakdown spectroscopy has been extensively tested in this kind of applications, this study presents an alternative method in terms of controlling the laser cleaning process of metallic object as well as real time laser-induced breakdown spectroscopy monitoring of the emission signal of the ablated material (pollutants and the structural materials). Several experimental parameters such as interpulses delay time, second laser to target distance and second pulse energy delay have also been accomplished in ancient Alexandrian coins. An enhancement of the signal emission is observed when both cleaning and analyzing lasers are combined, while no spectra signal is achieved when both lasers are operating independently. The restoration of ancient object by means of both conventional and double pulse laser cleaning arrangements is also discussed.
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paper_title: LIPS and linear correlation analysis applied to the classification of Roman pottery Terra Sigillata

paper_content:

Archaeological ceramics Terra Sigillata manufactured in different production centres have been studied by laser-induced plasma spectroscopy (LIPS). The aim of this work was to establish a procedure for the rapid classification of these archaeological ceramics in function of their provenance through combination of LIPS and statistical methodologies. Representative emission spectra of the Hispanic, Gaulish and African groups of pottery were selected as references. The use of linear correlation allowed one to cluster the samples by quantitative comparison of LIP spectra, leading to a reliable assignment of Terra Sigillata pieces to origin centres.
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paper_title: Controlled laser cleaning of painted artworks using accurate beam manipulation and on-line LIBS-detection

paper_content:

Abstract An innovative laser restoration tool for non-contact cleaning of painted artworks is developed. Accurate beam manipulation techniques in combination with on-line detection make the system suitable for selective cleaning of delicate surfaces. The utilisation of lasers obviates the use of various chemicals, and provides a method to remove layers that are untreatable using conventional methods. The first professional laser cleaning station for paintings is equipped with a modern mechatronic engineering tool for accurate beam manipulation (‘optical arm’). An intelligent combination of software and hardware enables accurate control, necessary to deal with the variable properties of the artworks to be treated. An on-line monitoring system is incorporated, using laser-induced breakdown spectroscopy. The user interface plays an important role in simulating the ‘hands-on’ treatment. In January 1999, the 2-year European co-operative research project ‘Advanced workstations for controlled laser cleaning of artworks’ started. The research objective is to define the boundary conditions in which laser cleaning with the present technology can be safely applied.
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paper_title: Theoretical Modeling of Laser Ablation of Quaternary Bronze Alloys: Case Studies Comparing Femtosecond and Nanosecond LIBS Experimental Data†

paper_content:

A model, formerly proposed and utilized to understand the formation of laser induced breakdown spectroscopy (LIBS) plasma upon irradiation with nanosecond laser pulses at different fluences and wavelengths, has been extended to the irradiation with femtosecond laser pulses in order to control the fractionation mechanisms which heavily affect the application of laser-ablation-based microanalytical techniques. The model takes into account the different chemico-physical processes occurring during the interaction of an ultrashort laser pulse with a metallic surface. In particular, a two-temperature description, relevant to the electrons and lattice of the substrate, respectively, has been introduced and applied to different ternary and quaternary copper-based alloys subjected to fs and ns ablation both in the visible (527 nm) and in the UV (248 nm). The model has been found able to reproduce the shorter plasma duration experimentally found upon fs laser ablation. Kinetic decay times of several copper (major e...
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paper_title: From LASER to LIBS, the path of technology development☆

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Abstract Laser-induced breakdown spectroscopy has made significant progress towards becoming a commercial, deployed technology. Its historical development will be reviewed, using the transformation of the laser into commercial technology as a parallel.
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paper_title: Laser assisted removal of synthetic painting-conservation materials using UV radiation of ns and fs pulse duration: Morphological studies on model samples

paper_content:

Abstract In an effort to establish the optimal parameters for the cleaning of complex layers of polymers (mainly based on acrylics, vinyls, epoxys known as Elvacite, Laropal, Paraloid B72, among others) applied during past conservation treatments on the surface of wall paintings, laser cleaning tests were performed with particular emphasis on the plausible morphological modifications induced in the remaining polymeric material. Pulse duration effects were studied using laser systems of different pulse durations ( ns and fs ) at 248 nm. Prior to tests on real fragments from the Monumental Cemetery in Pisa (Italy) which were coated with different polymers, attention was focused on the study of model samples consisting of analogous polymer films cast on quartz disks. Ultraviolet irradiation is strongly absorbed by the studied materials both in ns and fs irradiation regimes. However, it is demonstrated that ultrashort laser pulses result in reduced morphological alterations in comparison to ns irradiation. In addition, the dependence of the observed alterations on the chemical composition of the consolidation materials in both regimes was examined. Most importantly, it was shown that in this specific conservation problem, an optimum cleaning process may rely not only on the minimization of laser-induced morphological changes but also on the exploitation of the conditions that favour the disruption of the adhesion between the synthetic material and the painting.
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paper_title: Laser-induced breakdown spectroscopy for semi-quantitative and quantitative analyses of artworks—application on multi-layered ceramics and copper based alloys

paper_content:

Abstract In the present work, we report on the analyses of different types of artworks, such as medieval glazed Umbrian pottery and copper based alloys from Roman and modern periods, performed by means of Laser Induced Breakdown Spectroscopy (LIBS). The semi-quantitative analyses on the multi-layered ceramic findings regard glaze, luster and pigment decorations present on the surface. The composition for each decorative layer was determined by estimating the contribution of the ceramic layer beneath the examined one to the whole plasma emission. Two types of ancient luster have been considered: red and gold, while the pigments examined include painted decorations of different blue tonalities. The measured elemental composition of the decorative layers resulted partially correlated with the color of the painted surface, measured by a standard UV-VIS spectrometer. In LIBS analyses of bronze samples, a procedure was developed, which improves data repeatability and extends quantitative measurements to minor elemental constituents. Results of the quantitative analyses gave indications about the manufacturing process of the artwork, its actual degree of conservation and the presence of residual surface decorations.
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paper_title: Laser cleaning of terracotta decorations of the portal of Palos of the Cathedral of Seville

paper_content:

Abstract Laser cleaning has been used to restore the soiled terracotta statues and decorations of the tympanum of the portal of Palos of the Cathedral of Seville in Spain. A simultaneous laboratory study performed on a representative sample helped to identify the optimum laser conditions to remove the dark soiling layer produced by air pollution. It was found that irradiation at 1064 nm with a Q-switched Nd:YAG laser was more effective than the harmonic wavelengths of 532 or 266 nm. LIBS and Raman microscopy gave information on the composition of terracotta and identified the presence of a protective layer made of gypsum and calcite. As detected by Raman spectroscopy, laser irradiation caused the elimination of the carbon component of the soiling layer and the appearance of an anhydrite component in the laser irradiated gypsum layer applied over the terracotta substrate for protective purposes. Local heating of the surface caused by laser irradiation at 1064 nm, the laser wavelength used for restoration of the portal, might be responsible for a process of partial dehydration of gypsum into anhydrite.
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paper_title: Particle size distributions and compositions of aerosols produced by near-IR femto- and nanosecond laser ablation of brass

paper_content:

Particle size distributions and compositions of primary aerosols produced by means of near-IR femtosecond laser ablation (λ ::: = 775 nm) of brass in He or Ar at atmospheric pressure have been measured. Aerosols were characterized using a 13-stage low-pressure impactor covering a size range from 5 nm up to 5 μm and subsequently analyzed applying total reflection X-ray fluorescence spectrometry. The results indicate, that for femtosecond laser ablation in the low-fluence regime (<5 J cm−2) ultra-fine aerosols (mean diameter dp ::: ≈ 10 nm/peak width wp ::: ≈ 35 nm) are produced. Furthermore, the total Cu/Zn ratio of these aerosols corresponds to the composition of the bulk material. In contrast, ablation above 10 J cm−2 results in the formation of polydisperse, bimodal aerosols, which are distributed around dp1 ::: ≈ 20 nm (wp1 ::: ≈ 50 nm) and dp2 ::: ≈ 1 μm (wp2 ::: ≈ 5 µm), respectively, and whose total Cu/Zn ratio slightly deviates from the bulk composition. In order to examine the influence of pulse duration on particle size distribution and aerosol composition, comparative measurements by means of near-IR nanosecond ablation were also performed. The data show that nanosecond ablation generally leads to an intensified formation of particles in the micrometer range. Moreover, the composition of these aerosols strongly departs from the stoichiometry of the bulk. Aspects concerning the formation of particles during ablation as well as implications for the element-selective analysis by inductively coupled plasma spectrometry are discussed.
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paper_title: LIBS as a diagnostic tool during the laser cleaning of copper based alloys: experimental results

paper_content:

In spite of difficulties in quantitative LIBS analysis on copper based alloys, the very low invasiveness of the technique strongly sustains attempts to use it with cultural heritage materials, including ancient bronzes. Analytical results obtained with calibration curves and a calibration free model are compared here on a set of ancient roman coins. An attempt is presented to monitor the laser ablation process on bronze coins and artificially aged standards during the cleaning. The double pulse technique showed that LIBS analytical results could benefit from synchronization between the UV laser sources used, respectively, for cleaning (266 nm) and for LIBS analysis (335 nm).
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paper_title: Pigment identification in paintings employing laser induced breakdown spectroscopy and Raman microscopy

paper_content:

Abstract Laser-induced breakdown spectroscopy (LIBS) was used in combination with Raman microscopy, for the identification of pigments in different types of painted works of art. More specifically, a 19th century post-Byzantine icon from Greece and two miniature paintings from France were examined and detailed spectral data are presented which lead to the identification of the pigments used. LIBS measurements yielded information on the presence of pigments or mixtures of pigments based on the characteristic emission from specific elements. Identification of most pigments was performed by Raman microscopy. As demonstrated in this work, the combined use of LIBS and Raman microscopy, two complementary techniques, leads to a detailed characterization of the paintings examined with respect to the pigments used.
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paper_title: High energy ions generated by laser driven Coulomb explosion of cluster

paper_content:

Abstract We present an analytical model and three dimensional particle simulations of intense laser interaction with a cluster of overdense plasma. When laser intensity is above a critical value, it blows off all of electrons from the cluster and forms a non-neutral ion cloud. During the Coulomb explosion of the ion cloud, ions acquire their energy. Ion energy spectra are discussed in detail for different densities and sizes of clusters with various laser intensities. It is shown that ultra-fast ions are produced for relatively large clusters, and that the ion energy becomes three times greater than the maximum electrostatic potential energy of the ion cloud. The laser driven Coulomb explosion of a cluster may provide a new high energy ion source.
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paper_title: Er:YAG laser: an innovative tool for controlled cleaning of old paintings: testing and evaluation

paper_content:

Abstract A cleaning method based on an Er:YAG laser system at 2.94 μm, highly absorbed by OH bonds, was tested for removal of over-paintings, varnishes and patina top-layers from various painted surfaces, including laboratory paint models and old paintings. The aim was to evaluate the efficiency, selectivity and safety of the laser cleaning method using various pulse energies and various OH containing wetting agents to enhance the efficacy and limit the penetration of the laser beam. A large number of paint models were prepared with known characteristics (type and number of layers, thickness, composition) simulating old masters’ techniques. A set of diagnostic controls was designed to study the effects of the laser radiation on the surface components, including morphological, optical and chemical examination and analyses. The aim was also to compare the laser method with the traditional solvent based procedures. Thresholds of safe energy were found for each type of surface layer such as varnishes and over-paintings. The results confirmed the suitability of the Er:YAG laser when used by qualified and expert conservators, especially in combination with traditional chemical and mechanical cleaning methods.
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paper_title: Pigment analysis in Bronze Age Aegean and Eastern Mediterranean painted plaster by laser-induced breakdown spectroscopy (LIBS)

paper_content:

Laser-Induced Breakdown Spectroscopy (LIBS) was used in the examination of Bronze Age painted plaster samples from several sites in the Aegean and Eastern Mediterranean. The elemental content of paint materials was determined in most cases leading to the identification of the pigment used in agreement with data from analyses of the same samples with other established techniques. The analyses demonstrate that a virtually non-destructive technique such as LIBS provides sufficient data for the elemental characterisation of painting materials while in parallel has the capability for routine, rapid analysis of archaeological objects enabling the quick characterisation or screening of different types of artefacts. This certainly shows an important way forward in technological studies of fragile and scarce archaeological material.
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paper_title: Near-crater discoloration of white lead in wall paintings during laser induced breakdown spectroscopy analysis

paper_content:

Abstract During Laser-Induced Breakdown Spectroscopy (LIBS) analysis of white lead pigment (basic lead carbonate, 2PbCO3·Pb(OH)2), used in wall paintings of historical interest, a yellow–brown discoloration has been observed around the crater. This phenomenon faded after a few days exposure under ambient atmosphere. It was established that the mechanism of this discoloration consists in lead oxides (PbO) formation. It was verified by further experiments under argon atmosphere that recombination of lead with oxygen in the plasma plume produces the oxides, which settle around the crater and induce this discoloration. The impact of discoloration on the artwork's aesthetic aspect and the role of atmosphere on discoloration attenuation are discussed. The mechanism is studied on three other pigments (malachite, Prussian blue and ultramarine blue) and threshold for discoloration occurrence is estimated.
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paper_title: Short free running Nd:YAG laser to clean different encrustations on Pentelic marble: procedure and evaluation of the effects

paper_content:

Abstract On ancient Greek monuments of Pentelic marble, environmentally induced encrustation (black dendritic and thin) along with layers with ancient treatments (patina) were irradiated with a Nd:YAG laser system operating at the fundamental mode ( λ = 1064 nm) with t d = 20 μs (short free running Nd:YAG laser). Laser experiments were coupled with the spraying of small quantities of distilled water on the encrustation before the irradiation. The effects of the laser-assisted cleaning were investigated using thin section analysis, optical microscopy, scanning electron microscopy coupled to energy dispersive X-ray analysis, infrared spectroscopic analysis, and X-ray diffraction analysis, as well as color measurements and imaging analysis using multi-spectral imaging. Based on the results, the main evaluation criteria were achieved for the application of the short free running Nd:YAG laser system for cleaning purposes. Multi-spectral imaging enables the evaluation of color and textural changes and, therefore, can be considered as an appropriate tool for the in situ monitoring of the cleaning process.
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paper_title: Chronocultural sorting of archaeological bronze objects using laser-induced breakdown spectrometry

paper_content:

This work discusses the capability of laser-induced breakdown spectrometry (LIBS) for characterization and cataloging of metallic objects belonging to the Bronze and Iron Ages. A set of 37 metallic objects from different locations of the South East of Iberian Peninsula has been sorted according to their metal content. Arsenic concentration in metallic objects has been found a key factor for distinguishing between Bronze and Iron Ages objects, allowing the chronocultural sorting of each piece. For this study, a pulsed Q-switched Nd:YAG laser was used to generate a microplasma onto the sample surface. To quantify and catalogue these metallic objects, calibration curves for copper, arsenic, tin, lead and iron were established. The quantitative results demonstrate that the chronological sorting carried out by LIBS matches agreeably with archaeological dating criteria.
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paper_title: Use of LIBS for rapid characterization of parchment.

paper_content:

Parchment from different sources has been analyzed by laser-induced breakdown spectroscopy (LIBS) for determination of Ca, Na, K, Mg, Fe, Cu, and Mn. The LIBS results were compared with results from inductively coupled plasma spectroscopy (ICP) and good correlation was obtained. Rapid distinction between modern and historical samples was achieved by discriminant analysis of the LIBS data. Animal type recognition was also possible on the basis of Mg/Cu emission peak ratio and Mg depth profiling.
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paper_title: Spectroscopic analysis of works of art using a single LIBS and pulsed Raman setup.

paper_content:

A nanosecond pulsed laser setup has been optimized to perform laser-induced breakdown spectroscopy (LIBS) and pulsed Raman spectroscopy measurements in the field of cultural heritage. Three different samples of artistic/architectural interest with different typologies have been analyzed. The results from the two techniques allowed the identification of the materials used in their manufacture or contaminating them, probably coming from atmospheric pollution and biological activity. No sampling and sample preparation was required before the measurements, and no visual or structural damage was observed. Depth profiling using LIBS was performed in one of the samples, providing elemental information along the different layers composing the object and covering its surface. The quality of the results and the rather short time needed for the measurements and for switching between techniques confirmed the instrument's capabilities and specificity for dealing with objects of artistic or historical interest.
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paper_title: Remote imaging laser-induced breakdown spectroscopy and remote cultural heritage ablative cleaning

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We report, for what we believe to be the first time, on remote imaging laser-induced breakdown spectroscopy (LIBS). Measurements have been performed by using a tripled Nd:YAG laser working at 355 nm with 170 mJ pulse energy, with an expanded beam that is focused onto a target at 60 m distance. The LIBS signal is detected by using an on-axis Newtonian telescope and an optical multichannel analyzer. The imaging is performed by scanning the laser beam on the target. The same setup is also used in demonstrations of remote laser ablation for cleaning of contaminated objects with applications toward cultural heritage.
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paper_title: Pigment identification by spectroscopic means: an arts/science interface

paper_content:

Abstract Pigment identification on manuscripts, paintings, ceramics and papyri is critical in finding solutions to problems of restoration, conservation, dating and authentication in the art world. The techniques (molecular and elemental) used for these purposes are reviewed and compared, particular attention being given to Raman microscopy and laser-induced breakdown spectroscopy. These give excellent results in respect of reproducibility, sensitivity, non-destructiveness, immunity to interference from adjacent materials, and depth-profile analysis. New advances in optics provide powerful and long needed links for Arts- and Science-based projects. To cite this article: R.J.H. Clark, C. R. Chimie 5 (2002) 7–20
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paper_title: Analysis of pigments in polychromes by use of laser induced breakdown spectroscopy and Raman microscopy

paper_content:

Abstract Two laser-based analytical techniques, Laser Induced Breakdown Spectroscopy (LIBS) and Raman microscopy, have been used for the identification of pigments on a polychrome from the Rococo period. Detailed spectral data are presented from analyses performed on a fragment of a gilded altarpiece from the church of Escatron, Zaragoza, Spain. LIBS measurements yielded elemental analytical data which suggest the presence of certain pigments and, in addition, provide information on the stratigraphy of the paint layers. Identification of most pigments and of the materials used in the preparation layer was performed by Raman microscopy.
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paper_title: Application of the laser ablation for conservation of historical paper documents

paper_content:

Abstract Laser ablation was applied for surface cleaning and spectroscopic diagnostics of historical paper documents and model samples in the framework of the conservation projects. During cleaning the spectra of ablation products were recorded by means of the LIBS technique which allowed for nearly non-destructive identification of surface layers such as contaminants, substrate and pigments. For consecutive laser pulses a strong decrease of band intensities of the emission lines of Ca, Na, K, Al and Fe ascribed to contaminants were observed. The effect was used for monitoring of the cleaning progress of stained paper. For surface cleaning and spectra excitation the Q-switched Nd:YAG laser of 6 ns pulsewidth operating at wavelengths of 266, 355, 532, and 1064 nm and of fluence selected from the range 0.3–0.9 J/cm 2 was applied. The ablation parameters were optimized in agreement with the literature and the results were confirmed by surface studies and testing of the mechanical and chemical properties, and also by the response to the ageing process of the paper substrate. In case of the model paper irradiated in the UV range at 266 and 355 nm a visual inspection revealed local damages of the cellulose fibers accompanied by a decrease of the mechanical strength of the substrate. The effect was more pronounced after artificial ageing. The best results were obtained for samples irradiated at 532 nm and at laser fluence below the damage threshold of 0.6 J/cm 2 , which is in agreement with literature.
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paper_title: An example of the complementarity of laser-induced breakdown spectroscopy and Raman microscopy for wall painting pigments analysis

paper_content:

layer-by-layer analysis through a precise laser ablation of the sample. This work deals with the behavior of pigments after a LIBS analysis, by trying to identify the compounds before and after the laser shot. Six commercial pigments prepared with the fresco technique were investigated: ultramarine blue, red lead, charcoal, a yellow and a red ochre, and a green earth. Raman spectra, acquired on the sample surface and in the crater induced by LIBS analysis, were compared. The results show that these pigments are well recognized after a LIBS measurement. The analysis of green earth illustrates that the combination of these two techniques gives complete information from a sample. Copyright  2007 John Wiley & Sons, Ltd.
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paper_title: A comparison of nanosecond and femtosecond laser-induced plasma spectroscopy of brass samples

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The ablation of brass samples in argon shield gas by 170 fs and 6 ns laser pulses has been studied by optical emission spectroscopy of the evolving plasmas. Differences observed in the temporal behavior of the spectral line intensities are explained by the shielding effect of the Ar plasma for ns-pulses and the free expansion of the plasma of the ablated material in case of fs-pulses. Brass with different ZnrCu ratios were used as samples. Different types of crater formation mechanisms in the case of ns- and fs-pulses were observed. At 40 mbar argon pressure the thresholds of ablation were found to be ; 0.1 and ; 1.5 J cm y2 for fs- and ns-pulses, respectively. With an internal standardization of zinc to copper it is possible to correct for differences in the ablation rates and to obtain linear calibration curves. For optimum experimental conditions, narrower confidence intervals for the determination of unknown concentrations were found in case of fs-pulses. Within the range of the laser intensities used, no dependence of the ZnrCu line intensity ratio on the number of laser pulses applied to the same ablation spot was observed, neither for fs- nor for ns-pulses, which is interpreted as the absence of fractional vaporization. Q 2000 Elsevier Science B.V. All rights reserved.
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paper_title: Laser-induced breakdown spectroscopy (LIBS) in archaeological science—applications and prospects

paper_content:

Laser-induced breakdown spectroscopy (LIBS) has emerged in the past ten years as a promising technique for analysis and characterization of the composition of a broad variety of objects of cultural heritage including painted artworks, icons, polychromes, pottery, sculpture, and metal, glass, and stone artifacts. This article describes in brief the basic principles and technological aspects of LIBS, and reviews several test cases that demonstrate the applicability and prospects of LIBS in the field of archaeological science.
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paper_title: LIBS-spectroscopy for monitoring and control of the laser cleaning process of stone and medieval glass

paper_content:

Abstract On-line monitoring or even closed-loop control is necessary to avoid over-cleaning in case the ablation process is not self-limiting. Therefore, the laser-induced breakdown spectroscopy (LIBS) was used. Basic investigations were carried out on original sandstone samples ( Elbsandstein ) with strong encrustations as well as medieval stained glass samples (13th century from Cologne Cathedral). The spectroscopic study has shown that the plasma emission can be used for determination of the elemental composition of the ablated material. The plasma was initiated by 248-nm pulses of an KrF-excimer laser (30 ns FWHM). For the spectroscopic analysis, a grating spectrograph in combination with an optical multichannel analyser was used. For the glass and stone samples we obtained a continual alteration of the LIBS spectrum (vanishing of peaks and generating of new element peaks) during the removal process. Thus, certain element peaks can be used to distinguish between encrustation layer and valuable underlying material. To show the potential of LIBS we designed an experimental laser cleaning set-up including closed-loop LIBS control and demonstrated successful automatic cleaning of an original glass fragment.
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paper_title: Quantitative laser induced breakdown spectroscopy analysis of ancient marbles and corrections for the variability of plasma parameters and of ablation rate

paper_content:

White marble samples from ancient quarries have been analyzed by Laser Induced Breakdown Spectroscopy (LIBS) both on the bulk material and surface encrustations. With the aim to achieve quantitative results by LIBS, until now not reported on marble materials, calibration standards with CaCO3 matrices doped with certified soils were realized. Very different emission intensities and plasma parameters were observed on the standards and natural marbles. In order to compare so different spectra, a method for data analysis was developed, which takes into account variability of the ablation rate, plasma temperature and electron density. It was experimentally demonstrated that ablated volume is well correlated to the emission intensity of plasma continuum for a wide range of laser energies. LIBS signal normalization on the adjacent continuum level, together with introduction of correction factors dependent on plasma parameters, allowed the measuring of concentrations both for major and trace elements in marbles. The analytical procedure was validated by comparative SEM-EDX and ICP-OES measurements. Quantitative LIBS analyses were also performed during encrustation removal and could be applied to control laser-cleaning processes. The quantification of metal contents in the encrustations supported the occurrence of sulfates in the outer layers exposed to environmental agents via a catalytic process.
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paper_title: Controlled UV laser cleaning of painted artworks: a systematic effect study on egg tempera paint samples

paper_content:

Abstract The Cooperative Research project “Advanced workstation for controlled laser cleaning of artworks” (ENV4-CT98-0787) has yielded important information on the application of UV laser cleaning to paint materials. In the project, in which conservators, researchers and engineers participated, the viability of the laser technique as an additional tool in present conservation practice was investigated. The research was pointed at the definition of the boundary conditions in which laser cleaning can be safely applied. It included a systematic effect study of tempera paint systems. Physical and chemical changes, induced by exposure to UV (248 nm) excimer laser light under various conditions, were evaluated. In parallel, an innovative laser cleaning tool was developed, allowing accurate and controlled removal of superficial layers from paint materials. Both aspects of the project are presented. The presentation of the research focuses on the integration of the results from various analytical techniques, yielding valuable information on the immediate and long-term effects of UV laser radiation on the paint materials. The analytical techniques include colorimetry, spectroscopic techniques, mass spectrometry and profilometry, as well as thermographic and UV transmission measurements. Furthermore, the application of the laser workstation on various painted artworks is shown. This includes the gradual removal of varnish layers and the recovery of original paint colour in fire-damaged paintings.
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paper_title: ns- and fs-LIBS of copper-based-alloys: A different approach

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A self-calibrated analytical technique, based on plasmas induced by either 250 fs or 7 ns laser pulses, is presented. This approach is comparable to other calibration-free methods based on LTE assumption. In order to apply this method to very different laser pulse durations, the partial-local thermodynamic equilibrium (p-LTE) has been considered within the energy range of 30,000-50,000 cm -1 . In order to obtain the neutral species densities, the detected plasma species emission lines intensities have been treated together with the experimental evaluated background black-body Planck-like emission distribution. For validating the followed method, three certified copper-based-alloys standards were employed and their minor components (Ni, Pb and Sn) amounts were determined. As a result, it arises, that this standardless method, independently from the laser source pulse durations, provides good quantitative analysis, and, consequently, that the composition of the plasma plume emitting species induced is not affected by the laser pulse time width.
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paper_title: Laser Induced Breakdown Spectroscopy methodology for the analysis of copper-based-alloys used in ancient artworks☆

paper_content:

Abstract In this paper Laser Induced Breakdown Spectroscopy has been applied for determining the elemental composition of a set of ancient bronze artworks coming from archaeological site of Minervino Murge — Southern of Italy (dated around VII b.C.). Before carrying on the analysis of the archaeological samples, the characterization of the analytical technique has been accomplished by investigating the trueness of the typical assumptions adopted in LIBS, such as Local Thermodynamic Equilibrium, congruent ablation and plasma homogeneity. With this purpose, two different laser pulse durations, 7 ns and 350 fs, have been used. We have focused our attention on LIBS analysis of bronze standards by considering and discussing the bases of both methodology and analytical approach to be followed for the analysis of ancient copper-based-alloy samples. Unexpectedly, regardless from the laser pulse duration, the LIBS technique has shown, by considering an adequate approach on the emitting plasma features, that its peculiarities are anyway preserved so that a fast analysis of ancient copper-based-alloys can be achieved. After verifying the suitability of the methodology, it has been possible to fulfill the typical assumptions considered for the LIBS calibration curves method and use it for ancient bronze artworks analysis.
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paper_title: Compositional analysis of Hispanic Terra Sigillata by laser-induced breakdown spectroscopy

paper_content:

Abstract Laser induced breakdown spectroscopy (LIBS) has been applied for the analysis of Roman pottery Hispanic Terra Sigillata dating back to the 1st–5th century A.C. from two important ceramic production centers in Spain. For each sample, several examinations were performed on slip and body providing data necessary to draw depth profiles of the contents of various elements. In all the cases investigated, the amount of some elements such as calcium and iron and the presence of other ones such as silicon and aluminum showed the differences existing between slip and body in these ancient ceramics in relation with their region and period of production. In addition, complementary analyses were carried out with scanning electron microscopy linked with energy dispersive X-ray microanalysis (SEM/EDX) to measure the thickness of slip and to obtain verification of chemical results.
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paper_title: Effects of crater development on fractionation and signal intensity during laser ablation inductively coupled plasma mass spectrometry

paper_content:

Abstract The effects of crater development on ICP-MS signal intensities and elemental fractionation have been presented in this work. Craters formed after repetitive 266-nm Nd/YAG laser ablation with 1.0-mJ pulses had a cone-like shape. The laser ablation rate (ng/s) depended on the laser irradiance (laser pulse energy per unit time and unit area), decreasing as irradiance increased. In contrast, the particle entrainment/transport efficiency did not significantly change with irradiance. As the crater-aspect ratio (depth/diameter) increased above some threshold value of six, the Pb/U elemental ratio departed from the stoichiometric value. However, good stoichiometry of ablated mass could be achieved when experimental conditions were carefully selected. The exact mechanism of how crater development affects fractionation is not well understood. In this work, actual irradiance was introduced instead of a nominal value. Actual irradiance decreased as the crater deepened due to changes of the effective area, sampled by the laser beam.
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paper_title: LIBS analysis of geomaterials: Geochemical fingerprinting for the rapid analysis and discrimination of minerals

paper_content:

Abstract Laser-induced breakdown spectroscopy (LIBS) is a simple atomic emission spectroscopy technique capable of real-time, essentially non-destructive determination of the elemental composition of any substance (solid, liquid, or gas). LIBS, which is presently undergoing rapid research and development as a technology for geochemical analysis, has attractive potential as a field tool for rapid man-portable and/or stand-off chemical analysis. In LIBS, a pulsed laser beam is focused such that energy absorption produces a high-temperature microplasma at the sample surface resulting in the dissociation and ionization of small amounts of material, with both continuum and atomic/ionic emission generated by the plasma during cooling. A broadband spectrometer-detector is used to spectrally and temporally resolve the light from the plasma and record the intensity of elemental emission lines. Because the technique is simultaneously sensitive to all elements, a single laser shot can be used to track the spectral intensity of specific elements or record the broadband LIBS emission spectra, which are unique chemical ‘fingerprints’ of a material. In this study, a broad spectrum of geological materials was analyzed using a commercial bench-top LIBS system with broadband detection from ∼200 to 965 nm, with multiple single-shot spectra acquired. The subsequent use of statistical signal processing approaches to rapidly identify and classify samples highlights the potential of LIBS for ‘geochemical fingerprinting’ in a variety of geochemical, mineralogical, and environmental applications that would benefit from either real-time or in-field chemical analysis.
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paper_title: TRACE ELEMENT INPUTS INTO SOILS BY ANTHROPOGENIC ACTIVITIES AND IMPLICATIONS FOR HUMAN HEALTH

paper_content:

Trace element definition and functions, and inputs into soils from the most important anthropogenic sources, related and not related to agricultural practices, of general and local or incidental concern, are discussed in the first part of this review. Trace element inputs include those from commercial fertilizers, liming materials and agrochemicals, sewage sludges and other wastes used as soil amendments, irrigation waters, and atmospheric depositions from urban, industrial, and other sources. In the second part of the review, the most important ascertained effects of soil trace elements on human health are presented. The possible relations found between some specific soil trace elements, such as Cd, Se, As and others, and cancer incidence and mortality, and diffusion of other important human diseases are reviewed. Brief conclusions and recommendations conclude this review.
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paper_title: TRACE ELEMENT INPUTS INTO SOILS BY ANTHROPOGENIC ACTIVITIES AND IMPLICATIONS FOR HUMAN HEALTH

paper_content:

Trace element definition and functions, and inputs into soils from the most important anthropogenic sources, related and not related to agricultural practices, of general and local or incidental concern, are discussed in the first part of this review. Trace element inputs include those from commercial fertilizers, liming materials and agrochemicals, sewage sludges and other wastes used as soil amendments, irrigation waters, and atmospheric depositions from urban, industrial, and other sources. In the second part of the review, the most important ascertained effects of soil trace elements on human health are presented. The possible relations found between some specific soil trace elements, such as Cd, Se, As and others, and cancer incidence and mortality, and diffusion of other important human diseases are reviewed. Brief conclusions and recommendations conclude this review.
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paper_title: Mapping of lead, magnesium and copper accumulation in plant tissues by laser-induced breakdown spectroscopy and laser-ablation inductively coupled plasma mass spectrometry

paper_content:

article i nfo Laser-Induced Breakdown Spectroscopy (LIBS) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) were utilized for mapping the accumulation of Pb, Mg and Cu with a resolution up to 200 μm in a up to cm×cm area of sunflower (Helianthus annuus L.) leaves. The results obtained by LIBS and LA-ICP-MS are compared with the outcomes from Atomic Absorption Spectrometry (AAS) and Thin- Layer Chromatography (TLC). It is shown that laser-ablation based analytical methods can substitute or supplement these techniques mainly in the cases when a fast multi-elemental mapping of a large sample area is needed.
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paper_title: Quantitative analysis of arsenic in mine tailing soils using double pulse-laser induced breakdown spectroscopy

paper_content:

Abstract A double pulse-laser induced breakdown spectroscopy (DP-LIBS) was used to determine arsenic (As) concentration in 16 soil samples collected from 5 different mine tailing sites in Korea. We showed that the use of double pulse laser led to enhancements of signal intensity (by 13% on average) and signal-to-noise ratio of As emission lines (by 165% on average) with smaller relative standard deviation compared to single pulse laser approach. We believe this occurred because the second laser pulse in the rarefied atmosphere produced by the first pulse led to the increase of plasma temperature and populations of exited levels. An internal standardization method using a Fe emission line provided a better correlation and sensitivity between As concentration and the DP-LIBS signal than any other elements used. The Fe was known as one of the major components in current soil samples, and its concentration varied not substantially. The As concentration determined by the DP-LIBS was compared with that obtained by atomic absorption spectrometry (AAS) to evaluate the current LIBS system. They are correlated with a correlation coefficient of 0.94. The As concentration by the DP-LIBS was underestimated in the high concentration range (>1000 mg-As/kg). The loss of sensitivity that occurred at high concentrations could be explained by self-absorption in the generated plasma.
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paper_title: Evaluation of laser induced breakdown spectroscopy for cadmium determination in soils

paper_content:

Abstract Cadmium is known to be a toxic agent that accumulates in the living organisms and present high toxicity potential over lifetime. Efforts towards the development of methods for microanalysis of environmental samples, including the determination of this element by graphite furnace atomic absorption spectrometry (GFAAS), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma-mass spectrometry (ICP-MS) techniques, have been increasing. Laser induced breakdown spectroscopy (LIBS) is an emerging technique dedicated to microanalysis and there is a lack of information dealing with the determination of cadmium. The aim of this work is to demonstrate the feasibility of LIBS for cadmium detection in soils. The experimental setup was designed using a laser Q-switched (Nd:YAG, 10 Hz, λ = 1064 nm) and the emission signals were collimated by lenses into an optical fiber coupled to a high-resolution intensified charge-coupled device (ICCD)-echelle spectrometer. Samples were cryogenically ground and thereafter pelletized before LIBS analysis. Best results were achieved by exploring a test portion (i.e. sampling spots) with larger surface area, which contributes to diminish the uncertainty due to element specific microheterogeneity. Calibration curves for cadmium determination were achieved using certified reference materials. The metrological figures of merit indicate that LIBS can be recommended for screening of cadmium contamination in soils.
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paper_title: Determination of heavy metals in soils by Laser Induced Breakdown Spectroscopy

paper_content:

Laser Induced Breakdown Spectroscopy (LIBS) is a recent analytical technique that is based upon the measurement of emission lines generated by atomic species close to the surface of the sample, thus allowing their chemical identification. In this work, the LIBS technique has been applied to the determination of total contents of heavy metals in a number of reference soil samples. In order to validate the technique, LIBS data were compared with data obtained on the same soil samples by application of conventional Inductively Coupled Plasma (ICP) spectroscopy. The partial agreement obtained between the two sets of data suggested the potential applicability of the LIBS technique to the measurement of heavy metals in soils.
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paper_title: Utilization of laser induced breakdown spectroscopy for investigation of the metal accumulation in vegetal tissues

paper_content:

We report on the development and implementation of analytical methodology for investigating elemental accumulation in different layers within plant leaves, with in-situ spatial resolution mapping, exploiting the technique of LIBS. The spectrochemical analysis of lead-doped leaf samples is demonstrated to develop a real time identification procedure in order to complement other analytical techniques not lending themselves for spatial resolution analysis. Our findings suggest that with elevated levels of Pb within the plants transportation and storage of some nutrition elements is changed.
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paper_title: Towards quantitative laser-induced breakdown spectroscopy analysis of soil samples ☆

paper_content:

A quantitative analysis of chromium in soil samples is presented. Different emission lines related to chromium are studied in order to select the best one for quantitative features. Important matrix effects are demonstrated from one soil to the other, preventing any prediction of concentration in different soils on the basis of a univariate calibration curve. Finally, a classification of the LIBS data based on a series of Principal Component Analyses (PCA) is applied to a reduced dataset of selected spectral lines related to the major chemical elements in the soils. LIBS data of heterogeneous soils appear to be widely dispersed, which leads to a reconsideration of the sampling step in the analysis process.
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paper_title: Measurement Of Nutrients In Green House Soil With Laser Induced Breakdown Spectroscopy

paper_content:

Laser-induced breakdown spectroscopy (LIBS) has been applied for the determination of nutrients in the green house soil samples. We determined appropriate spectral signatures of vital nutrients and calibrated the method to measure the nutrients in a naturally fertilized plot, cultivated with tomato and cucumber plants. From the calibration curves we predicted the concentrations of important nutrients such as Ca, K, P, Mg, Fe, S, Ni and Ba in the soil. Our measurements proved that the LIBS method rapidly and efficiently measures soil nutrients with excellent detection limits of 12, 9, 7, 9, 7, 10, 8 and 12~mg/kg for Ca, K, P, Mg, Fe, S, Ni and Ba respectively with a precision of 2%, The unique features of LIBS for rapid sample analysis demonstrated by this study suggests that this method offers promise for precision measurements of soil nutrients as compared to conventional methods in short span of time.
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paper_title: Studying the enhanced phytoremediation of lead contaminated soils via laser induced breakdown spectroscopy

paper_content:

Abstract Phytoremediation popularly known as 'green clean technology' is a new promising technology used for toxic contaminants removal from the environment such as heavy metals (HMs), adopting suitable plants. This concept is increasingly being adopted as it is a cost effective and environmentally friendly alternative to traditional methods of treatment. This study was focused on using scented geranium, Pelargonium zonale , as accumulator or hyperaccumulator plant for natural lead extraction from artificially contaminated soil with different Pb concentrations (0, 2000, 5000, 7000 ppm). Utilization of EDTA as a chelator, that would permit higher metal availability and uptake by the tested plants roots, was also tested. Laser Induced Breakdown Spectroscopy (LIBS) was used to follow up Pb concentrations in both soil and plant green harvestable parts known as shoots, before, during and after lead addition in soil. LIBS measurements were conducted in a microdestructive way by focusing a high energy Nd:YAG laser, emitting at 1064 nm, on plant and soil samples previously dried, homogenized and pressed in pellets. The emitted LIBS spectra were acquired by a gated CCD after dispersion on a monochromator and analyzed to retrieve relative concentrations of the selected HM both in the soil and on plants as a function of the time after doping and eventual chelator addition. EDTA was found to enhance Pb uptake from the soil which increased with time, good correlation was found between LIBS and ICP-OES results of plant tissues spectrochemical analysis.
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paper_title: Enrichment and depletion of major and trace elements, and radionuclides in ombrotrophic raw peat and corresponding humic acids

paper_content:

Abstract An ombrotrophic peat core (10 × 10 × 81 cm) was collected from Etang de la Gruere (Switzerland) and divided in 27 slices of 3 cm. Humic acids (HAs) were extracted from each slice after freeze-drying and fine milling. All raw peat and HA samples were analyzed using Energy-dispersive miniprobe X-ray fluorescence multielement analyser (EMMA-XRF), fluorescence spectroscopy and Low Background γ-spectrometry (LB γ-spec). The abundance and distribution of major and trace elements and radionuclides were measured in raw peat and corresponding HAs to possibly evaluate their affinity for organic ligands and establish which organic fraction might affect their behaviour along the profile. Raw peat samples show higher concentrations of Fe, Mn, Pb, Sr, Ti and Ca in comparison to the corresponding HAs, while Cu is more abundant in HAs. Zinc presents greater concentrations in raw peat in the first 24 cm of depth. All elements, with the exception of Fe, seem to be bound stably to HAs, although at different extent. The activity of 241 Am is limited to the raw peat of a specific section of the profile, while that of 137 Cs is recorded both in HAs and raw peat, even below the depth one would expect, suggesting the scarce mobility of the former and a different impact of these radionuclides on the environment.
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paper_title: Monitoring and assessment of toxic metals in Gulf War oil spill contaminated soil using laser-induced breakdown spectroscopy

paper_content:

Laser-induced breakdown spectroscopy (LIBS) was applied for the detection of toxic metals in oil spill contaminated soil (OSCS). The OSCS samples were collected from Khursania Saudi Arabia along the coast of Persian Gulf exposed to oil spills in 1991 Gulf war. Environmentally important elements like Aluminum Magnesium, Calcium, Chromium, Titanium, Strontium, Iron, Barium, Sodium, potassium, Zirconium and Vanadium from the contaminated soil have been detected. Optimal experimental conditions for analysis were investigated. The LIBS system was calibrated using standard samples containing these trace elements. The results obtained using Laser-Induced Breakdown Spectroscopy (LIBS) were compared with the results obtained using Inductively Coupled Plasma Emission Spectroscopy (ICP). The concentrations of some elements (Ba and Cr) were found higher than permissible safe limits. Health risks associated with exposure to such toxic elements are also discussed.
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paper_title: Analysis of lead and sulfur in environmental samples by double pulse laser induced breakdown spectroscopy

paper_content:

In the present work, a model of double pulse laser-induced breakdown spectroscopy (LIBS) spectrometer has been developed and results from two different applications of double pulse LIBS for solving the problems of environmental interest are presented. In one case, laser induced breakdown spectroscopy has been applied to the determination of heavy and toxic metals (lead) in soil samples. In the second case, laser induced breakdown spectroscopy was used in preliminary experiments for the detection of sulfur content in coal, and on the basis of spectral features, ways to improve the sensitivity of laser induced breakdown spectroscopy detection of sulfur are proposed. The detection limit for lead in soil was estimated to be approximately 20 ppm that is lower than the regulatory standards for the presence of lead in soil.
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paper_title: Measuring Total Soil Carbon with Laser-Induced Breakdown Spectroscopy (LIBS)

paper_content:

Improving estimates of carbon inventories in soils is currently hindered by lack of a rapid analysis method for total soil carbon. A rapid, accurate, and precise method that could be used in the field would be a significant benefit to researchers investigating carbon cycling in soils and dynamics of soil carbon in global change processes. We tested a new analysis method for predicting total soil carbon using laser-induced breakdown spectroscopy (LIBS). We determined appropriate spectral signatures and calibrated the method using measurements from dry combustion of a Mollisol from a cultivated plot. From this calibration curve we predicted carbon concentrations in additional samples from the same soil and from an Alfisol collected in a semiarid woodland and compared these predictions with additional dry combustion measurements. Our initial tests suggest that the LIBS method rapidly and efficiently measures soil carbon with excellent detection limits (∼300 mg/kg), precision (4-5%), and accuracy (3-14%). Initial testing shows that LIBS measurements and dry combustion analyses are highly correlated (adjusted r 2 = 0.96) for soils of distinct morphology, and that a sample can be analyzed by LIBS in less than one minute. The LIBS method is readily adaptable to a field-portable instrument, and this attribute-in combination with rapid and accurate sample analysis-suggests that this new method offers promise for improving measurement of total soil carbon. Additional testing of LIBS is required to understand the effects of soil properties such as texture, moisture content, and mineralogical composition (i.e., silicon content) on LIBS measurements.
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paper_title: Laser-induced breakdown spectroscopy for the environmental determination of total carbon and nitrogen in soils.

paper_content:

Soils from various sites have been analysed with the laser-induced breakdown spectroscopy (LIBS) technique for total elemental determination of carbon and nitrogen. Results from LIBS have been correlated to a standard laboratory-based technique (sample combustion), and strong linear correlations were obtained for determination of carbon concentrations. The LIBES technique was used on soils before and after acid washing, and the technique appears to be useful for the determination of both organic and inorganic soil carbon. The LIBS technique has the potential to be packaged into a field-deployable instrument.
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paper_title: Real time and in situ determination of lead in road sediments using a man-portable laser-induced breakdown spectroscopy analyzer

paper_content:

Abstract In situ, real time levels of lead in road sediments have been measured using a man-portable laser-induced breakdown spectroscopy analyzer. The instrument consists of a backpack and a probe housing a Q-switched Nd:YAG laser head delivering 50 mJ per pulse at 1064 nm. Plasma emission was collected and transmitted via fiber optic to a compact cross Czerny-Turner spectrometer equipped with a linear CCD array allocated in the backpack together with a personal computer. The limit of detection (LOD) for lead and the precision measured in the laboratory were 190 μg g −1 (calculated by the 3σ method) and 9% R.S.D. (relative standard deviation), respectively. During the field campaign, averaged Pb concentration in the sediments were ranging from 480 μg g −1 to 660 μg g −1 depending on the inspected area, i.e. the entrance, the central part and the exit of the tunnel. These results were compared with those obtained with flame-atomic absorption spectrometry (flame-AAS). The relative error, expressed as [100(LIBS result − flame AAS result)/(LIBS result)], was approximately 14%.
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paper_title: Development of a mobile system based on laser-induced breakdown spectroscopy and dedicated to in situ analysis of polluted soils ☆

paper_content:

Principal Components Analysis (PCA) is successfully applied to the full laser-induced breakdown spectroscopy (LIBS) spectra of soil samples, defining classes according to the concentrations of the major elements. The large variability of the LIBS data is related to the heterogeneity of the samples and the representativeness of the data is finally discussed. Then, the development of a mobile LIBS system dedicated to the in-situ analysis of soils polluted by heavy metals is described. Based on the use of ten-meter long optical fibers, the mobile system allows deported measurements. Finally, the laser-assisted drying process studied by the use of a customized laser has not been retained to overcome the problem of moisture.
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paper_title: Double pulse, calibration-free laser-induced breakdown spectroscopy: A new technique for in situ standard-less analysis of polluted soils

paper_content:

Laser-induced breakdown spectroscopy (LIBS) is a promising technique for in situ environmental analysis. The potential of this technique for accurate quantitative analysis could be greatly improved using an innovative experimental setup – based on the use of two laser pulses suitably retarded – and analyzing the results with a standard-less procedure which overcomes the problems related to matrix effects. A new mobile instrument for soil analysis, developed at the Applied Laser Spectroscopy Laboratory in Pisa, is presented, and some experimental results are given.
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paper_title: Analysis of environmental lead contamination: comparison of LIBS field and laboratory instruments

paper_content:

Abstract The Army Research Office of the Army Research Laboratory recently sponsored the development of a commercial laser-induced breakdown spectroscopy (LIBS) chemical sensor that is sufficiently compact and robust for use in the field. This portable unit was developed primarily for the rapid, non-destructive detection of lead (Pb) in soils and in paint. In order to better characterize the portable system, a comparative study was undertaken in which the performance of the portable system was compared with a laboratory LIBS system at the Army Research Laboratory that employs a much more sophisticated laser and detector. The particular focus of this study was to determine the effects on the performance of the field sensor's lower spectral resolution, lack of detector gating, and the multiple laser pulsing that occurs when using a passively Q-switched laser. Surprisingly, both the laboratory and portable LIBS systems exhibited similar performance with regards to detection of Pb in both soils and in paint over the 0.05–1% concentration levels. This implies that for samples similar to those studied here, high-temporal resolution time gating of the detector is not necessary for quantitative analysis by LIBS. It was also observed that the multiple pulsing of the laser did not have a significant positive or negative effect on the measurement of Pb concentrations. The alternative of using other Pb lines besides the strong 406-nm line was also investigated. No other Pb line was superior in strength to the 406-nm line for the latex paint and the type of soils used in the study, although the emission line at 220 nm in the UV portion of the spectrum holds potential for avoiding elemental interferences. These results are very encouraging for the development of lightweight, portable LIBS sensors that use less expensive and less sophisticated laser and detector components. The portable LIBS system was also field tested successfully at sites of documented Pb contamination on military installations in California and Colorado.
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paper_title: Artificial neural network for Cu quantitative determination in soil using a portable Laser Induced Breakdown Spectroscopy system

paper_content:

Abstract Laser Induced Breakdown Spectroscopy (LIBS) is an advanced analytical technique for elemental determination based on direct measurement of optical emission of excited species on a laser induced plasma. In the realm of elemental analysis, LIBS has great potential to accomplish direct analysis independently of physical sample state (solid, liquid or gas). Presently, LIBS has been easily employed for qualitative analysis, nevertheless, in order to perform quantitative analysis, some effort is still required since calibration represents a difficult issue. Artificial neural network (ANN) is a machine learning paradigm inspired on biological nervous systems. Recently, ANNs have been used in many applications and its classification and prediction capabilities are especially useful for spectral analysis. In this paper an ANN was used as calibration strategy for LIBS, aiming Cu determination in soil samples. Spectra of 59 samples from a heterogenic set of reference soil samples and their respective Cu concentration were used for calibration and validation. Simple linear regression (SLR) and wrapper approach were the two strategies employed to select a set of wavelengths for ANN learning. Cross validation was applied, following ANN training, for verification of prediction accuracy. The ANN showed good efficiency for Cu predictions although the features of portable instrumentation employed. The proposed method presented a limit of detection (LOD) of 2.3 mg dm − 3 of Cu and a mean squared error (MSE) of 0.5 for the predictions.
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paper_title: On board LIBS analysis of marine sediments collected during the XVI Italian campaign in Antarctica

paper_content:

Abstract The Laser-induced Breakdown Spectroscopy technique was applied on board the R/V Italica during the XVI Antarctic campaign (2000–2001) to carry out elemental chemical analysis of marine sediments collected using different sampling systems. To this end, a compact system has been built, which was suitable to operate also in the presence of mechanical vibrations, induced by the ship motion. Qualitative and quantitative analyses were performed on dried samples, without any further pre-treatment. Qualitative analyses have shown similar elemental composition among different collected sediments, except for significant differences in the case of rock fragments and manganese nodule. The latter also contains some heavy metals that in sediment layers were detected only in traces. The methodology to retrieve relative or absolute elemental concentration in heterogenous samples has been optimized and is scarcely sensitive to variations of sediment physical properties with depth, and to experimental parameters such as laser defocusing because of surface irregularities, and laser energy fluctuations. The relative distribution of the major elemental constituents, both from a bio-organic and mineral origin, was measured as a function of sediment depth. Measurements, once limited to specific spectral sections, and data analyses are fast and very reproducible. Most of the elements show a gradually varying distribution along the sampled core, except for silicon and barium, whose steep decrease with depth is strongly related to their biogenic origin. Quantitative LIBS analyses were performed on a limited number of samples and the results reported here, are comparable to the certified element contents in a reference sample of Antarctic sediments.
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paper_title: Design, construction and assessment of a field-deployable laser-induced breakdown spectrometer for remote elemental sensing

paper_content:

A field-deployable laser-induced breakdown spectrometer for measurements in the hundreds of meters range has been presented. The system is capable of elemental analysis with no previous preparation and in near real time, with the only requirement of a free line-of-sight between the instrument and the sample. Main factors influencing LIBS performance at stand-off distances are outlined. LIBS signal is shown to depend on range of analysis, peak power, beam quality, laser wavelength and optics dimensions. A careful control of focusing conditions has been shown to be of importance to avoid interferences from air breakdown by the stand-off focused beam.
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paper_title: Remote laser-induced plasma spectrometry for elemental analysis of samples of environmental interest

paper_content:

Remote laser-induced plasma spectrometry has been demonstrated as a valuable analytical tool both for qualitative inspection and quantitative determinations on environmental samples. For this objective, the pulsed radiation of a Q-switched Nd:YAG laser at 1064 nm has been used to produce a plasma in a remote sample, the light emission being collected under a coaxial open-path optical scheme and guided towards a spectrograph and then detected by an intensified CCD. A prospective study has been carried out to assess the suitability of the technique for the remote analysis of samples from a coastal scenario subjected to a high industrial activity. All the measurements have been done in the laboratory. Among the main factors influencing the analytical results, sample moisture and salinity, sample orientation and surface heterogeneity have been identified. The presence and distribution of Fe and Cr as a contaminant on sample surface has been quantified and discussed for samples including soil, rocks, and vegetation. At a stand-off distance of 12 m from the spectrometer to the sample, limits of detection in the order of 0.2% have been obtained for both elements.
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paper_title: LIBS-an efficient approach for the determination of Cr in industrial wastewater.

paper_content:

In the present paper, LIB spectra of different water samples having varying concentration of Cr (certified reference material, CRM) have been recorded by using liquid jet (fabricated in our laboratory) configuration. Calibration curves for different atomic lines of Cr are compared and it is found that calibration curve for Cr II (283.5 nm) atomic line is the best in terms of the Limit of detection (LOD) which is found to be 30 ppm. This calibration curve has been used for quantification of Cr in wastewater collected from Cr-electroplating industry where the concentration of Cr is found to be 1500 ppm. Its removal can be planned by biological system, which is in progress.
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paper_title: Detection of Toxic Metals in Waste Water from Dairy Products Plant Using Laser Induced Breakdown Spectroscopy

paper_content:

Laser Induced Breakdown Spectroscopy (LIBS) System was developed locally for determination of toxic metals in liquid samples and the system was tested for analysis of waste water collected from dairy products processing plant. The plasma was generated by focusing a pulsed Nd: YAG laser at 1064 nm on waste water samples. Optimal experimental conditions were evaluated for improving the sensitivity of our LIBS system through parametric dependence investigations. The Laser-Induced Breakdown Spectroscopy (LIBS) results were then compared with the results obtained using standard analytical technique such as Inductively Coupled Plasma Emission Spectroscopy (ICP). The evaluation of the potential and capabilities of LIBS as a rapid tool for liquid sample analysis are discussed in brief.
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paper_title: Double-pulse LIBS in bulk water and on submerged bronze samples

paper_content:

In this work laser-induced breakdown spectroscopy (LIBS) has been applied in bulk water using a double-pulse laser source. As in the case of former experiments in air, the use of the double-pulse technique allows for enhancing line emission intensity and reducing the duration of the continuum spectrum, thus increasing the overall analytical performances of the technique. Tap water analysis of Na and Mg dissolved cations has been performed to investigate the capability of the technique, but most significant results have been obtained in determining the composition of submerged bronze targets by laser ablation of their surface in seawater. When the plasma is generated by double-pulse laser, the ablated matter is strongly confined by the water vapor inside the cavitations bubble. The confinement of the plasma leads to higher values of excitation temperature and holds the conditions suitable for chemical analysis (homogeneity and LTE) longer than what happens in gaseous media. The double-pulse experiments performed directly in bulk water point out the features of LIBS technique for real analytical applications in situ, such as the water quality assessment and the investigation of irremovable submerged objects.
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paper_title: Single Pulse-Laser Induced Breakdown Spectroscopy in aqueous solution

paper_content:

In this paper the flexibility of Laser Induced Breakdown Spectroscopy (LIBS) has been proved for the analysis of water solutions. The plasma is generated directly in the bulk of a water solution by a Q-switched Nd:YAG laser (1064). The emission signal of four different solutions has been studied: AlCl3, NaCl, CaCO3 and LiF. The basic mechanisms influencing the emission signal and the experimental tricks for the optimization of the detection mode have been pointed out.
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paper_title: From single pulse to double pulse ns-Laser Induced Breakdown Spectroscopy under water : Elemental analysis of aqueous solutions and submerged solid samples

paper_content:

Abstract In this paper the developments of Laser Induced Breakdown Spectroscopy (LIBS) underwater have been reviewed to clear up the basic aspects of this technique as well as the main peculiarities of the analytical approach. The strong limits of Single-Pulse (SP) LIBS are discussed on the basis of plasma emission spectroscopy observations, while the fundamental improvements obtained by means of the Double-Pulse (DP) technique are reported from both the experimental and theoretical point of view in order to give a complete description of DP-LIBS in bulk water and on submerged solid targets. Finally a detailed description of laser–water interaction and laser-induced bubble evolution is reported to point out the effect of the internal conditions (radius, pressure and temperature) of the first pulse induced bubble on the second pulse producing plasma. The optimization of the DP-LIBS emission signal and the determination of the lower detection limit, in a set of experiments reported in the current scientific literature, clearly demonstrate the feasibility and the advantages of this technique for underwater applications.
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paper_title: Double pulse laser-induced breakdown spectroscopy of bulk aqueous solutions at oceanic pressures: interrelationship of gate delay, pulse energies, interpulse delay, and pressure.

paper_content:

Laser-induced breakdown spectroscopy (LIBS) has been identified as an analytical chemistry technique suitable for field use. We use double pulse LIBS to detect five analytes (sodium, manganese, calcium, magnesium, and potassium) that are of key importance in understanding the chemistry of deep ocean hydrothermal vent fluids as well as mixtures of vent fluids and seawater. The high pressure aqueous environment of the deep ocean is simulated in the laboratory, and the key double pulse experimental parameters (laser pulse energies, gate delay time, and interpulse delay time) are studied at pressures up to 2.76x10(7) Pa. Each element is found to have a unique optimal set of parameters for detection. For all pressures and energies, a short (< or = 100 ns) gate delay is necessary. As pressure increases, a shorter interpulse delay is needed and the double pulse conditions effectively become single pulse for both the 1.38x10(7) Pa and the 2.76x10(7) Pa conditions tested. Calibration curves reveal the limits of detection of the elements (5000 ppm Mg, 500 ppm K, 500 ppm Ca, 1000 ppm Mn, and 50 ppm Na) in aqueous solutions at 2.76x10(7) Pa for the experimental setup used. When compared to our previous single pulse LIBS work for Ca, Mn, and Na, the use of double pulse LIBS for analyte detection in high pressure aqueous solutions did not improve the limits of detection.
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paper_title: Laser-induced breakdown spectroscopy of bulk aqueous solutions at oceanic pressures: evaluation of key measurement parameters.

paper_content:

The development of in situ chemical sensors is critical for present-day expeditionary oceanography and the new mode of ocean observing systems that we are entering. New sensors take a significant amount of time to develop; ::: therefore, validation of techniques in the laboratory for use in the ocean environment is necessary. Laser-induced breakdown spectroscopy (LIBS) is a promising in situ technique for oceanography. Laboratory investigations on the feasibility of using LIBS to detect analytes in bulk liquids at oceanic pressures were carried out. LIBS was successfully used to detect dissolved Na, Mn, Ca, K, and Li at pressures up to ::: 2.76×107 Pa. The effects of pressure, laser-pulse energy, interpulse delay, gate delay, temperature, and NaCl concentration on the LIBS signal were examined. An optimal range of laser-pulse energies was found to exist for analyte detection in bulk aqueous solutions at both low and high pressures. No pressure effect was seen on the emission intensity for Ca and Na, and an increase in emission intensity with increased pressure was seen for Mn. Using the dual-pulse technique for several analytes, a very short interpulse delay resulted in the greatest emission intensity. The presence of NaCl enhanced the emission intensity for Ca, but had no effect on peak intensity of Mn or K. Overall, increased pressure, the addition of NaCl to a solution, and temperature did not inhibit detection of analytes in solution and sometimes even enhanced the ability to detect the analytes. The results suggest that LIBS is a viable chemical sensing method for in situ analyte detection in high-pressure environments such as the deep ocean.
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paper_title: Comparisons between LIBS and ICP/OES

paper_content:

In the framework of the development of new techniques, the ability of laser-induced breakdown spectroscopy (LIBS) to analyse remotely complex aqueous solutions was investigated. The jet configuration with a collimated gas stream was chosen because it appeared to be the most promising method for the LIBS probe, particularly in terms of sensitivity and repeatability. For emission collection, the echelle spectrometer offers a simultaneously recorded wavelength range from the UV to the near IR and is interesting for multielemental analysis for LIBS and also for inductively coupled plasma (ICP) optical emission spectroscopy (OES). The importance of parameters influencing the quantitative results of LIBS such as multispecies analysis, sheath gas, use of an internal standard and temporal parameters for analysis is described. LIBS quantitative data have been directly compared with results from the more standard ICP/OES technique.
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paper_title: Detection of chromium in liquids by laser induced breakdown spectroscopy (LIBS)

paper_content:

Environmental concerns about the amount of dissolved heavy metals in coastal tidal waters have led to investigations into possible ways to detect chromium dissolved in water. A method using fluorescence spectroscopy in solution has been proposed. However, such optical emission spectroscopic methods tend to suffer from a lack of sensitivity caused by the strong quenching processes in liquids. In this investigation, Nd:YAG Q-switched laser pulses were utilised to generate a plasma filled bubble in a chromium solution. Fluorescence in the plasma was detected using an optical fibre tip placed adjacent to the bubble. Light wavelengths characteristic of chromium were detected and spectral images recorded using an optical multi-channel analyzer.
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paper_title: ArF Laser-Induced Plasma Spectroscopy for Part-per-Billion Analysis of Metal Ions in Aqueous Solutions

paper_content:

Aqueous samples containing trace amounts of metal ions in 0.8 M HCl were ablated with an ArF laser. Plasma emissions were monitored for elemental analysis. The signal-to-noise ratio was optimized when the laser fluence was about 10 J cm-2, while the detector gate delay and width were 1-2 μs and 3-4 μs, respectively. During that time, the temperature and electron density of the induced plasma were also measured spectroscopically. The temperature dropped from about 0.5 to about 0.3 eV, while the density remained fairly constant at about 3 × 1016 cm-3. Background-free spectrochemical analysis was therefore possible. The detection limits for Na, Ca, Ba, and Pb were 0.4, 3, 7, and 300 ppb, respectively. These are 20 to 1000 times better than the best achieved by non-193-nm laser-induced breakdown spectroscopy.
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paper_title: Laser induced breakdown spectroscopy of soils, rocks and ice at subzero temperatures in simulated martian conditions

paper_content:

Abstract We applied Laser Induced Breakdown Spectroscopy (LIBS) on moist soil/rock samples in simulated Martian conditions. The signal behavior as a function of the surface temperature in the range from + 25 °C to − 60 °C was studied at pressure of 7 mbar. We observed the strong signal oscillations below 0 °C with different negative peaks, whose position, width and magnitude depend on the surface roughness. In some cases, the signal was reduced for one order of magnitude with consequences for the LIBS analytical capability. We attribute such a signal behavior to the presence of supercooled water inside the surface pores, which freezing point depends on the pore size. On a same rock samples with different grades of the surface polishing, the signal has different temperature dependence. Its decrease was always registered close to 0 °C, corresponding to the freezing/melting of normal disordered ice, which can be present inside larger pores and scratching. An amount of the signal reduction at the phase transition temperatures does not seem to change with the laser energy density in the examined range. Comparative measurements were performed on a frozen water solution. A large depression, for two orders of magnitude, of the LIBS intensity was observed close to − 50 °C. The same negative peak, but with a smaller magnitude, was also registered on some rock/soil samples. Ablation rates and plasma parameters as a function of the sample temperature are also discussed, and their consequences for in-situ analyses.
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paper_title: Spectral analysis of two Perseid meteors

paper_content:

Abstract Spectra of two bright ( −11 mag) Perseid meteors are studied. Monochromatic light curves are constructed and the spectra are analyzed at selected points along the trajectory. The shift of maxima of low excitation iron lines down the trajectory in meteor flares is observed and explained by a longer radiative lifetime of the upper levels for these lines. Two spectral components with the temperatures of 4400–4800 K and 10,000 K, respectively, are identified in the spectra in accordance with previous findings. The ratio of both components, in terms of mass, varied smoothly from about 100:1 over 15:1 to 30:1. This ratio is not an unambiguous function of meteor velocity, height and brightness but depends on the previous evolution of ablation. The abundances of heavy elements are found consistent with the chemical composition of carbonaceous chondrites and the dust of comet Halley. Hydrogen, however, is not more abundant than in carbonaceous chondrites and thus significantly less than in cometary dust. The initial masses of the two meteoroids are estimated at 40 and 80 g, respectively. The meteor V-band luminous efficiency is found to vary in the range log τ v = −11.8 to −12.0 in magnitude c.g.s. units. For the panchromatic luminous efficiency use of the value of −11.4 for bright Perseids is recommended. Nearly 1.5% of meteoroid kinetic energy is radiated out in the Ca II lines and 1 % in all other lines between 3500 and 6600 A.
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paper_title: Laser-induced breakdown spectroscopy for space exploration applications: Influence of the ambient pressure on the calibration curves prepared from soil and clay samples

paper_content:

Abstract Recently, there has been an increasing interest in the laser-induced breakdown spectroscopy (LIBS) technique for stand-off detection of geological samples for use on landers and rovers to Mars, and for other space applications. For space missions, LIBS analysis capabilities must be investigated and instrumental development is required to take into account constraints such as size, weight, power and the effect of environmental atmosphere (pressure and ambient gas) on flight instrument performance. In this paper, we study the in-situ LIBS method at reduced pressure (7 Torr CO 2 to simulate the Martian atmosphere) and near vacuum (50 mTorr in air to begin to simulate the Moon or asteroids' pressure) as well as at atmospheric pressure in air (for Earth conditions and comparison). Here in-situ corresponds to distances on the order of 150 mm in contrast to stand-off analysis at distance of many meters. We show the influence of the ambient pressure on the calibration curves prepared from certified soil and clay pellets. In order to detect simultaneously all the elements commonly observed in terrestrial soils, we used an Echelle spectrograph. The results are discussed in terms of calibration curves, measurement precision, plasma light collection system efficiency and matrix effects.
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paper_title: Laser induced breakdown spectroscopy on soils and rocks: Influence of the sample temperature, moisture and roughness

paper_content:

Abstract ExoMars, ESA's next mission to Mars, will include a combined Raman/LIBS instrument for the comprehensive in-situ mineralogical and elemental analyses of Martian rocks and soils. It is inferred that water exists in the upper Martian surface as ice layers, “crystal” water or adsorbed pore water. Thus, we studied Laser Induced Breakdown Spectroscopy (LIBS) on wet and dry rocks under Martian environmental conditions in the temperature range − 60 °C to + 20 °C and in two pressure regimes, above and below the water triple point. Above this point, the LIBS signals from the rock forming elements have local minima that are accompanied by hydrogen (water) emission maxima at certain temperatures that we associate with phase transitions of free or confined water/ice. At these sample temperatures, the plasma electron density and its temperature are slightly lowered. In contrast to powder samples, a general increase of the electron density upon cooling was observed on rock samples. By comparing the LIBS signal behavior from the same rock with different grades of polishing, and different rocks with the same surface treatment, it was possible to distinguish between the influence of surface roughness and the bulk material structure (pores and grains). Below the triple point of water, the LIBS signal from the major sample elements is almost independent of the sample temperature. However, at both considered pressures we observed a hydrogen emission peak close to − 50 °C, which is attributed to a phase transition of supercooled water trapped inside bulk pores.
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paper_title: Comparative study of different methodologies for quantitative rock analysis by Laser-Induced Breakdown Spectroscopy in a simulated Martian atmosphere

paper_content:

Laser-Induced Breakdown Spectroscopy was selected by NASA as part of the ChemCam instrument package for the Mars Science Laboratory rover to be launched in 2009. ChemCam's Laser-Induced Breakdown Spectroscopy instrument will ablate surface coatings from materials and measure the elemental composition of underlying rocks and soils at distances from 1 up to 10 m. The purpose of our studies is to develop an analytical methodology enabling identification and quantitative analysis of these geological materials in the context of the ChemCam's Laser-Induced Breakdown Spectroscopy instrument performance. The study presented here focuses on several terrestrial rock samples which were analyzed by Laser-Induced Breakdown Spectroscopy at an intermediate stand-off distance (3 m) and in an atmosphere similar to the Martian one (9 mbar CO2). The experimental results highlight the matrix effects and the measurement inaccuracies due to the noise accumulated when low signals are collected with a detector system such as an Echelle spectrometer equipped with an Intensified Charge-Coupled Device camera. Three different methods are evaluated to correct the matrix effects and to obtain quantitative results: by using an external reference sample and normalizing to the sum of all elemental concentrations, by using the internal standardization by oxygen, a major element common to all studied matrices, and by applying the Calibration Free Laser-Induced Breakdown Spectroscopy method. The three tested methods clearly demonstrate that the matrix effects can be corrected merely by taking into account the difference in the amount of vaporized atoms between the rocks, no significant variation in plasma excitation temperatures being observed. The encouraging results obtained by the three methods indicate the possibility of meeting ChemCam project objectives for stand-off quantitative analysis on Mars.
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paper_title: Investigation of LIBS feasibility for in situ planetary exploration: An analysis on Martian rock analogues

paper_content:

Abstract Laser induced breakdown spectroscopy (LIBS) has significant potential for remote terrestrial and extraterrestrial applications, nonetheless a number of correlated problems are still to be properly understood and possibly solved. This study focuses on several samples of terrestrial provenience, mostly volcanic rocks, which have importance as analogue to expected Martian samples. They were analysed after vaporisation with a frequency tripled Nd:YAG laser emitting at 355 nm , and measurements were made in an environment similar to the Martian one. Quantitative data were obtained by adopting the calibration free LIBS approach. A comparison with SEM-EDX data from the same samples is reported. Present results on Mars rocks analogues suggest that, in spite of residual interpretative ambiguities, LIBS technique permits elemental qualitative identification and quantitative analysis on silicate minerals examined in a rarefied atmosphere.
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paper_title: Chemical abundances determined from meteor spectra: I. Ratios of the main chemical elements

paper_content:

Relative chemical abundances of 13 meteoroids were determined by averaging the composition of the radiating gas along the fireball path that originated during their penetration into the Earth's atmosphere. Mg, Fe, Ni, Cr, Mn, and Co abundances, relative to Si, are similar to those reported for CI and CM carbonaceous chondrites and interplanetary dust particles. In contrast, relative abundances of Ca and Ti in meteor spectra indicate that these elements suffer incomplete evaporation processes. The chemical composition of all meteoroids studied in this work differs from that of 1P/Halley dust.
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paper_title: Use of the vacuum ultraviolet spectral region for laser-induced breakdown spectroscopy-based Martian geology and exploration

paper_content:

Abstract Several elements important to planetary geology (e.g. Br, C, Cl, P, S) and the human exploration of Mars (e.g. toxic elements such as As) have strong emission lines in the purge and vacuum ultraviolet (VUV) spectral region (100–200 nm). This spectral region has not been extensively studied for space applications using geological samples. We studied emissions from the laser-induced breakdown spectroscopy (LIBS) plasma in this region using a sample chamber filled with 7 torr (930 Pa) of CO 2 to simulate the Martian atmosphere. Pressures down to 0.02 torr were also used to evaluate the effect of the residual CO 2 on the spectra and to begin investigating the use of VUV-LIBS for airless bodies such as asteroids and the Moon. Spectra were recorded using a 0.3-m vacuum spectrometer with an intensified CCD (ICCD) camera. The effects of time delay and laser energy on LIBS detection at reduced pressure were examined. The effect of ambient CO 2 on the detection of C in soil was also evaluated. Lines useful for the spectrochemical analysis of As, Br, C, Cl, P, and S were determined and calibration curves were prepared for these elements. Although LIBS is being developed for stand-off analysis at many meters distance, the experiments reported here were aimed at in-situ (close-up) analysis.
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paper_title: Meteor luminosity simulation through laser ablation of meteorites

paper_content:

Light production mechanisms during ablation of meteors in planetary atmospheres are still not well understood. We have used a high-power pulsed (15 mJ per 10-ns pulse) Nd:YAG laser, frequency-doubled to 532-nm wavelength, to heat chondritic meteorite samples rapidly, and then used CCD imaging and spectral cameras to search for light produced by the rapidly heated meteorite vapour. We report here that light is produced by the rapidly heated and expanding ablated material without the need for collision with a high-speed atomic beam. The light production region is of the order of 2 mm in diameter. The light produced is a combination of either continuum or unresolved spectral line emission, along with spectral emission lines of Ca, Fe, Na, N, Mg, Si and O, with spectra from both neutral and singly ionized species. We have used a scanning electron microscope (SEM) to characterize the size of the ablated region (approximately 160 μm wide and 170 μm deep). The SEM, equipped with energy-dispersive X-ray spectroscopy, was also used to perform elemental analysis of our sample, which confirmed the presence of the identified elements in the original meteorite. The current experiments were done at room temperature and pressure, with mean power input rates that would correspond to low atmospheric penetration of meteorites. While others have used similar techniques for remote identification of elements present on surfaces in space and in meteorites, to our knowledge this is the first paper to propose laser ablation as a means of studying light production in modest-sized meteors.
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paper_title: Laser-Induced Breakdown Spectroscopy for Mars surface analysis: capabilities at stand-off distances and detection of chlorine and sulfur elements

paper_content:

Abstract An international consortium is studying the feasibility of performing in situ geochemical analysis of Mars soils and rocks at stand-off distances up to several meters using the Laser-Induced Breakdown Spectroscopy (LIBS) technique. Stand-off analysis for Martian exploration imposes particular requirements on instrumentation, and it is necessary to first test the performance of such a system in the laboratory. In this paper, we test the capabilities of two different experimental setups. The first one is dedicated to the qualitative analysis of metals and rocks at distances between 3 and 12 m. With the second one, we have obtained quantitative results for aluminum alloys and developed a spectral database under Martian conditions for sulfur and chlorine, two elements that are geologically interesting but generally difficult to detect by LIBS under standard conditions (atmospheric pressure, close distance). These studies were carried out to determine an optimal instrumental design for in situ Mars analysis. The quality of analytical results affected by the optical elements and spectrometer has been particularly highlighted.
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paper_title: Analysis of Water Ice and Water Ice/Soil Mixtures Using Laser-Induced Breakdown Spectroscopy: Application to Mars Polar Exploration

paper_content:

Recently, laser-induced breakdown spectroscopy (LIBS) has been developed for the elemental analysis of geological samples for application to space exploration. There is also interest in using the technique for the analysis of water ice and ice/dust mixtures located at the Mars polar regions. The application is a compact instrument for a lander or rover to the Martian poles to interrogate stratified layers of ice and dusts that contain a record of past geologic history, believed to date back several million years. Here we present results of a study of the use of LIBS for the analysis of water ice and ice/dust mixtures in situ and at short stand-off distances (< 6.5 m) using experimental parameters appropriate for a compact instrument. Characteristics of LIBS spectra of water ice, ice/soil mixtures, element detection limits, and the ability to ablate through ice samples to monitor subsurface dust deposits are discussed.
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paper_title: The Cambridge Encyclopedia of Meteorites

paper_content:

Foreword 1. Cosmic dust - interplanetary dust particles 2. The fall of meteorites 3. External morphology of meteorites 4. Classification of meteorites: a historical viewpoint 5. Primitive meteorites: the chondrites 6. Chondrites: a closer look 7. Primitive meteorites: the carbonaceous chondrites 8. Differentiated meteorites: the achondrites 9. Differentiated meteorites: irons and stony-irons 10. Meteorites and the early solar system 11. Asteroid parent bodies 12. Terrestrial impact craters Appendices.
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paper_title: Feasibility of generating a useful laser-induced breakdown spectroscopy plasma on rocks at high pressure: preliminary study for a Venus mission

paper_content:

Abstract Laser-induced breakdown spectroscopy (LIBS) is being developed for future use on landers and rovers to Mars. The method also has potential for use on probes to other planets, the Moon, asteroids and comets. Like Mars, Venus is of strong interest because of its proximity to earth, but unlike Mars, conditions at the surface are far more hostile with temperatures in excess of 700 K and pressures on the order of 9.1 MPa (90 atm). These conditions present a significant challenge to spacecraft design and demand that rapid methods of chemical data gathering be implemented. The advantages of LIBS (e.g. stand-off and very rapid analysis) make the method particularly attractive for Venus exploration because of the expected short operational lifetimes (≈2 h) of surface instrumentation. Although the high temperature of Venus should pose no problem to the analytical capabilities of the LIBS spark, the demonstrated strong dependence of laser plasma characteristics on ambient gas pressures below earth atmospheric pressure requires that LIBS measurements be evaluated at the high Venus surface pressures. Here, we present a preliminary investigation of LIBS at 9.1 MPa for application to the analysis of a basalt rock sample. The results suggest the feasibility of the method for a Venus surface probe and that further study is justified.
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paper_title: What can We Learn about Atmospheric Meteor Ablation and Light Production from Laser Ablation

paper_content:

Laboratory based laser ablation techniques can be used to study the size of the luminous region, predict spectral features, estimate the luminous efficiency factor, and assess the role of chemically differentiated thermal ablation. A pulsed Nd:YAG laser was used to ablate regions from ordinary and carbonaceous chondrite meteorites. CCD cameras and a digital spectroscope were used to measure the size and spectrum from the cloud of vaporised material. Scanning electron microscope (SEM) based energy dispersive x-ray spectroscopy (EDS) provided elemental abundance values in ablated and unablated regions. These results indicated some degree of differential ablation, with the most significant effect being significant loss of carbon from carbonaceous chondrites. This work suggests that a carbon matrix may play the role of the glue in the two component dustball model.
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Title: Laser Induced Breakdown Spectroscopy for Elemental Analysis in Environmental, Cultural Heritage and Space Applications: A Review of Methods and Results

Section 1: Introduction
Description 1: Provide an overview of the development and fundamental principles of Laser Induced Breakdown Spectroscopy (LIBS), including its advantages and limitations.

Section 2: Basic Principles of LIP and LIBS
Description 2: Outline the basic principles of Laser-Induced Plasma (LIP) formation and the operational mechanics of LIBS, including experimental set-ups and configurations.

Section 3: Elemental Analysis by LIBS
Description 3: Discuss the fundamental assumptions and practical considerations in using LIBS for qualitative and quantitative elemental analysis.

Section 4: LIBS Approaches to Quantitative Analysis
Description 4: Detail the various methods for quantitative analysis using LIBS, including calibration line and calibration-free approaches.

Section 5: LIBS in Cultural Heritage Science
Description 5: Explore the applications of LIBS in cultural heritage, with examples of its use in analyzing archaeological and historical artifacts.

Section 6: LIBS in Environmental Science
Description 6: Discuss the applications of LIBS in environmental science, focusing on soil analysis and other related fields.

Section 7: Laboratory LIBS Analysis of Soils
Description 7: Detail the laboratory procedures and methodologies for analyzing soil samples using LIBS, including comparisons with other techniques.

Section 8: In situ LIBS Analysis of Soils
Description 8: Address the challenges and methodologies for performing in situ LIBS analysis of soil, including portable systems and matrix effects.

Section 9: Stand-off LIBS Analysis of Soils
Description 9: Describe the stand-off LIBS techniques for soil analysis, highlighting the capabilities and limitations in remote sensing applications.

Section 10: LIBS Analysis of Aqueous Samples
Description 10: Discuss the potential and challenges of using LIBS for analyzing aqueous samples, including wastewater and seawater.

Section 11: LIBS in Space Science
Description 11: Review the applications of LIBS in space exploration, including the analysis of extraterrestrial materials and in situ planetary exploration.

Section 12: Conclusions
Description 12: Summarize the review, highlighting the versatility and potential of LIBS across various fields of application, along with the main findings and future directions.