Kinetics of the Reaction of NO3 with HO2

Article abstract of DOI:10.1021/j100328a043

The kinetics of the title reaction were investigated by molecular modulation-UV/visible absorption spectroscopy.NO3 and HO2 were generated by modulated photolysis of Cl2 in the presence of ClONO2, H2, and O2 in a flow system at 1 atm pressure and their concentration modulations monitored by time-resolved absorption at 662 and 220 nm, respectively.The rate coefficient for the overall reaction NO3 + HO2 -> products, k₄, was determined by computer fitting to data at five temperatures in the range 263-338 K and was given by k₄ = (2.3^+2.8_-1.8) * 10^-12 exp(+(170 +/- 270)/T) cm³ molecule^-1 s^-1.An upper limit of 0.6 for the ratio k_4b/k at 283 K, where k_4b is the rate constant for the reaction channel NO3 + HO2 -> OH + NO2 + O2, was established by measurement of OH by modulated resonance absorption.The alternate channel, 4a, is assumed to produce HNO3, i.e., NO3 + HO2 -> HNO3 + O2.