Encyclopedia of Astrobiology

Living Edition

Photochemistry, Atmospheric

  • Melissa G. Trainer
Living reference work entry
DOI: https://doi.org/10.1007/978-3-642-27833-4_1194-3


Atmospheric photochemistry is the study of light initiated chemical reactions which occur in the atmospheres of planetary bodies. These reactions play an important role in climate, and likely contributed to prebiotic organic synthesis.


Planetary atmospheric photochemistry occurs when incident radiation contains enough energy to dissociate bonds within the atmospheric molecules. Bond energies in atmospheric molecules are on the order of 102–103 kJ mol−1, and thus bond dissociation requires photons in the ultraviolet and visible region of the electromagnetic spectrum. A photochemical reaction occurs when the absorption of light triggers an electronic transition within the molecule, activating the reaction. Products of photo dissociation are typically highly reactive radicals.

A photochemical reaction is represented by the following general equation:
$$ \mathrm{A}\mathrm{B}+\mathrm{h}\nu \to \mathrm{A}+\mathrm{B} $$


Quantum Yield Organic Synthesis Photon Flux Absorption Cross Section Photochemical Reaction 

References and Further Reading

  1. Brasseur GP, Solomon S (2005) Aeronomy of the middle atmosphere: chemistry and physics of the stratosphere and mesosphere, 3rd edn. Springer, DordrechtGoogle Scholar
  2. Seinfeld JH, Pandis SN (1998) Atmospheric chemistry and physics. Wiley, New YorkGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg (outside the USA) 2014

Authors and Affiliations

  1. 1.NASA Goddard Space Flight Center Code 699GreenbeltUSA