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Pure Appl. Chem. Vol.
73, No. 3, pp. 487-490 (2001)
Pure and Applied
Vol. 73, Issue
Important photochemical processes in the atmosphere*
Geert K. Moortgat
Max-Planck-Institut für Chemie, Atmospheric Chemistry
Department, P.O. Box 3060, D-55020 Mainz, Germany
Abstract: Among the many important roles played by ozone in
the atmosphere is the role it plays in the generation of OH radicals,
which are responsible for initiating the oxidation of a wide variety
of atmospheric trace constituents. The OH production occurs dominantly
from the formation of the excited O(1D) species in the UV photolysis
of ozone, followed by the reaction of O(1D) with H2O vapor. The photochemistry
of ozone is very complex, as the relatively weak bonds in ozone allow
different states of the O and O2 photoproducts to be accessed. Recent
detailed studies have now revealed that different photolysis channels
are occurring in the 290375 nm spectral range, the region of importance
for the generation of OH radicals in the lower atmosphere. The measured
temperature-dependent quantum yields for the production of O(1D) atoms
reflect the importance of the longer "wavelength tail" formation
with regard to the enhanced OH production. Other significant atmospheric
photolysis processes involving carbonyl compounds are reported. Direct
photodissociation rates were measured in the outdoor photoreactor EUPHORE
in Valencia and compared with model calculations. For most of the carbonyl
compounds the effective quantum yields are significantly below unity.
*Lecture presented at the XVIIIth IUPAC Symposium on
Photochemistry, Dresden, German , 22-27 July 2000.Other presentations
are published in this issue, pp.395-548.
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