Absorption of sunlight induces photochemistry and generates a variety of free radicals that drive the chemistry of the troposphere as well as the stratosphere. This chapter focuses on the absorption spectra and photochemistry of important atmospheric species. These data can be used in conjunction with the actinic fluxes described in the preceding chapter to estimate rates of photolysis of various molecules as well as the rate of generation of photolysis products, including free radicals, from these photochemical processes.
There are several highly useful sources of data on the absorption spectra and photochemistry of atmospheric species. NASA publishes on a regular basis a summary of kinetics and photochemical data directed to stratospheric chemistry (DeMore et al., 1997). However, much of the data is also relevant to the troposphere. This document can be obtained from the Jet Propulsion Laboratory in Pasadena, California. Alternatively, the data are available through the Internet (see Appendix IV). IUPAC also publishes regularly in The Journal of Physical Chemical Reference Data a summary directed more toward tropospheric chemistry (Atkinson et al., 1997a, 1997b). Finally, Nolle et al. (1999) have made available a CD-ROM containing the UV-visible spectra of species of atmospheric interest.
We do not attempt a comprehensive treatment of the literature on each of the compounds discussed herein. With apologies to our colleagues whose work may not be explicitly cited, we shall rely on these exhaustive evaluations carried out by NASA (DeMore et al., 1997) and IUPAC (Atkinson et al., 1997a, 1997b) whenever possible. The reader should consult these evaluations, in addition to the original literature after 1998, for details and more recent studies.
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