Near-UV photolysis cross sections of CH3OOH and HOCH2OOH determined via action spectroscopy C. M. Roehl1, Z. Marka1,*, J. L. Fry2,**, and P. O. Wennberg1,3 1Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA 2Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 91125, USA 3Division 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
Abstract. 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. For compounds yielding
OH, this method can be used to measure near-UV photodissociation cross
section as low as 10−23 cm2 molecule−1. The method is applied
to determine the photodissociation cross sections for methyl hydroperoxide
(CH3OOH; MHP) and hydroxymethyl hydroperoxide (HOCH2OOH; HMHP) in
the 305–365 nm wavelength range. The measured cross sections are in good
agreement with previous measurements of absorption cross sections.
Citation: Roehl, C. M., Marka, Z., Fry, J. L., and Wennberg, P. O.: Near-UV photolysis cross sections of CH3OOH and HOCH2OOH determined via action spectroscopy, Atmos. Chem. Phys., 7, 713-720, doi:10.5194/acp-7-713-2007, 2007.