KINETICS OF THE REACTION HO2+NO2(+M)=HO2NO2 USING MOLECULAR MODULATION SPECTROMETRY

Rate constants for the reaction HO2 + NO2(+ M) = HO2NO2(+ M) have been obtained from direct observations of the HO2 radical using the technique of molecular modulation ultraviolet spectrometry. HO2 was generated by periodic photolysis of Cl2 in the presence of excess H2 and O2, and k1 was determined from the measured concentrations and lifetime of HO2 with NO2 present. k1 increased with pressure in the range of 40–600 Torr, and a simple energy transfer model gave the following limiting second‐ and third‐order rate constants at 283 K: k1∞ = 1.5 ± 0.5 × 10−12 cm3/molec·sec and k1III = 2.5 ± 0.5 × 10−31 cm6/molec·sec. The ultraviolet absorption spectrum of peroxynitric acid was also recorded in the range of 195–265 nm; it showed a broad feature with a maximum at 200 nm, σmax = 4.4 × 10−18 cm2. Copyright © 1979 John Wiley & Sons, Inc.