Near-UV photolysis cross sections of CH3OOH and HOCH2OOH determined via action spectroscopy
- 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.