Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 7 3 2007 10.5194/acp-7-713-2007 http://www.atmos-chem-phys.net/7/713/2007/ http://www.atmos-chem-phys.net/7/713/2007/acp-7-713-2007.html http://www.atmos-chem-phys.net/7/713/2007/acp-7-713-2007.pdf 713 720 2007-02-14 Near-UV photolysis cross sections of CH₃OOH and HOCH₂OOH determined via action spectroscopy C. M. Roehl coleen@gps.caltech.edu Z. Marka J. L. Fry P. O. Wennberg Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA now at: Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027, USA now at: Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720-1460, USA Knowledge of molecular photolysis cross sections is important for determining atmospheric lifetimes and fates of many species. A method and laser apparatus for measurement of these cross sections in the near-ultraviolet (UV) region is described. The technique is based on action spectroscopy, where the yield of a photodissociation product (in this case OH) is measured as a function of excitation energy. 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