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International Journal of Photoenergy
Volume 7 (2005), Issue 2, Pages 61-70
Review article

Sunlight initiated atmospheric photochemical reactions

Department of Chemistry and Biochemistry and CIRES, University of Colorado, Boulder Campus Box 215, Boulder, Colorado 80309-0215, USA

Copyright © 2005 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The Sun is the light source driving atmospheric chemistry. The wavelengths dependent photon flux is controlled by solar emission modulated by absorption of atmospheric gases, aerosols and clouds. The factors determining the characteristics of this light source, its altitude, latitude and zenith angle dependence are discussed to explain the effectiveness of the Sun in driving chemical reactions. Examples of chemical reactions occurring on the excited and the ground electronic state potential energy surfaces of molecules and radicals are used to illustrate the complexity of atmospheric photochemistry. Specifically, the near ultraviolet (UV) photochemistry of chlorine dioxide is used to exemplify electronic state reactions occurring in the atmosphere. The near infrared (IR) photochemistry of nitric and sulfuric acids are discussed to illustrate reactions important in the atmosphere which occur with solar pumping of vibrational overtone transitions in the ground electronic state of these molecules.