Investigation into the pressure dependence between 1 and 10 Torr of the reactions of NO2 with CH3 and CH3O

Abstract

The kinetics and pressure dependence of the reactions of NO2 with CH3 and CH3O have been investigated in the gas phase at 298 K, at pressures from 1 to 10 Torr. A low-pressure discharge-flow laser-induced fluorescence (LIF) technique was used. In a consecutive process, CH3 reacted with NO2 to form CH3O, CH3+ NO2→ CH3O + NO (1), which further reacted with NO2 to form products, CH3O + NO2→ products (2). Reaction (1) displayed no discernible pressure dependence over the pressure range 1–7 Torr, and k1 was calculated to be (2.3 ± 0.3)× 10–11 cm3 molecule–1 s–1. Reaction (2) displayed a strong pressure dependence and an RRKM analysis yielded the following limiting low- and high-pressure rate constants in He, k0= 5.9 × 10–29 cm6 molecule–2 s–1 and k∞= 2.1 × 10–11 cm3 molecule–1 s–1. It is unrealistic to quote errors for this type of analysis. Parametrisation in the standard Troe form with Fc= 0.6 yielded k0=(5.3 ± 0.2)× 10–29 cm6 molecule–2 s–1 and k∞=(1.4 ± 0.1)× 10–11 cm3 molecule–1 s–1. Atmospheric implications and possible reaction mechanisms are discussed.