A variant of this technique was used in an experiment used to show the existence of gravitational redshift by Pound and Rebka.
A miniature device capable of utilizing this analytical technique for studying martian soil was present on both NASA rovers Spirit and Opportunity. A process analogous to the physical principle underlying this analytical technique necessitates the appearance of a zero-phonon peak on a plot of the optical absorbance of a sample of chromophores embedded in a solid matrix at low temperatures. Sodium nitroprusside is used as a common reference material in this type of spectroscopy where nuclei with spin-states greater than ½ experience a characteristic quadrupole splitting. A variant of this technique was used in an experiment used to show the existence of gravitational redshift by Pound and Rebka. For 10 points, name this technique which exploits the fact that a percentage of gamma-ray absorptions and emissions with nuclei are recoil-free, and can be used to probe oxidation states of iron-57 nuclei.
A miniature device capable of utilizing this analytical technique for studying martian soil was present on both NASA rovers Spirit and Opportunity.
Mossbauer Spectroscopy (ACCEPT: Iron-57 Mossbauer Spectroscopy and other reasonable prefixed nuclei until mention of iron-57)