INVESTIGATION INTO THE PRESSURE-DEPENDENCE BETWEEN 1 AND 10 TORR OF THE REACTIONS OF NO2 WITH CH3 AND CH3O

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 pressure s from 1 to 10 Torr. A low-pressure discharge-flow laser-induced fluor escence (LIF) technique was used. In a consecutive process, CH3 reacte d with NO2 to form CH3O, CH3 + NO2 --> CH3O + NO (1), which further re acted with NO2 to form products, CH3O + NO2 --> products (2). Reaction (1) displayed no discernible pressure dependence over the pressure ra nge 1-7 Torr, and k1 was calculated to be (2.3 +/- 0.3) x 10(-11) cm3 molecule-1 s-1. Reaction (2) displayed a strong pressure dependence an d an RRKM analysis yielded the following limiting low- and high-pressu re rate constants in He, k(o) = 5.9 x 10(-29) cm6 molecule-2 s-1 and k (infinity) = 2.1 x 10(-11) cm3 molecule-1 s-1. It is unrealistic to qu ote errors for this type of analysis. Parametrisation in the standard Troe form with F(c) = 0.6 yielded k(o) = (5.3 + 0.2) x 10(-29) cm-6 mo lecule-2 s-1 and k(infinity) = (1.4 + 0.1) x 10(-11) cm3 molecule-1 s- 1. Atmospheric implications and possible reaction mechanisms are discu ssed.