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

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) cm(2) 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.