CH3O Yield in the CH3+ O3Reaction Using the LP/LIF Technique at Room Temperature

Abstract

CH3O(X2E) radicals have been detected by laser-induced fluorescence (LIF) for the first time as a product of the reaction between CH3 and O3. CH3 radicals were generated by excimer-laser photolysis of CH3Br at 193 nm in the presence of O3 at room temperature and 100 Torr of He. The rate constant for reaction 1a (CH3 + O3 → CH3O + O2) has been determined by monitoring the CH3O build-up as a function of reaction time and k1a was found to be (9.68 ± 1.10) × 10-14 cm3 molecule-1 s-1. The rate coefficient of the global reaction 1 (CH3 + O3 → products) has been determined by the numerical analysis of the CH3O temporal profiles, yielding a value of k1 = (2.2 ± 0.3) × 10-12 cm3 molecule-1 s-1. Reaction of CH3 with NO2 has also been studied under the same experimental conditions as reaction 1 and has been used to calibrate the CH3O LIF signal. On the other hand, the rate constant k2 for reaction 2 (CH3O + O3 → products) has been directly determined (k2(T = 298 K) = (2.53 ± 0.75) × 10-14 cm3 molecule-1 s-1) using t...