Measurements of the Pressure Dependence of the HO2 Radical Self-Disproportionation Reaction at 298 K

Article abstract of DOI:10.1021/j100275a017

Flash photolysis kinetic absorption spectroscopy was used to investigate the gas-phase disproportionation reaction of hydroperoxy radicals at 298 K.Measurements of k1(? (where k1 is the rate constant and ? is the HO2 absorption cross section) were made as a function of N2 and O2 pressures between 25 and 600 torr.Our observations of the linear dependence of k1 on total pressure as well as of the exsistence of a finite bimolecular (zero-pressure) reaction component are in good agreement with other recent investigations.An analysis of our data using the equation k1=k₁⁰+k_N2+k_O2 yields k₁⁰=1.88*10^-12 cm³ molecule^-1 s^-1, k_N2=5.95*10^-32 cm⁶ molecule^-2 s^-1, and k_O2=4.53*10^-32 cm⁶ molecule^-2 s^-1.An error band of +/-20 percent is assigned for 95 percent confidence limits.Together with the earlier studies, the present work provides a detailed data base upon which to make rate constant recommendations for atmospheric modeling.