Photolysis of Sulfuric Acid Vapor by Visible Solar Radiation
V. Vaida,1*
H. G. Kjaergaard,2
P. E. Hintze,1
D. J. Donaldson3
Atmospheric field measurements and models of the
stratospheric sulfate aerosol layer led to the suggestion that sulfuric
acid (H2SO4) must photolyze at high altitudes.
We propose that excitation of vibrational overtones of
H2SO4 and its hydrate in the near-infrared and
visible leads to photolysis, forming sulfur trioxide (SO3) and water. On the basis of absorption cross sections calculated with ab
initio methods calibrated to experimental measurements, we estimated
J values that are sufficient to explain stratospheric and
mesospheric sulfur dioxide (SO2) concentrations and
the observation of the sulfate layer.
1 Department of Chemistry and Biochemistry and
Cooperative Institute for Research in Environmental Sciences (CIRES),
University of Colorado, Boulder, CO 80309-0215, USA.
2 Department of Chemistry, University of Otago, Post
Office Box 56, Dunedin, New Zealand.
3 Department of
Chemistry and University of Toronto at Scarborough, 80 St. George
Street, Toronto, ON M5S 3H6 Canada.
*
To whom correspondence should be addressed. E-mail:
vaida{at}colorado.edu
