INVESTIGATION INTO THE KINETICS AND MECHANISM OF THE REACTION OF NO3 WITH CH3 AND CH3O AT 298-K BETWEEN 0.6-TORR AND 8.5-TORR - IS THERE A CHAIN DECOMPOSITION MECHANISM IN OPERATION

The reactions CH3 + NO3 --> products (1), and CH3O + NO3 --> products (2), have been studied using a flow system at T = 298 K and at pressures between 0.6 and 8.5 Torr. The laser-induced fluorescence (LIF) technique was used to detect CH3O and multi-pass optical absorption to detect NO3. The chemical systems were studied as a pair of consecutive reactions; however, a simple analytical treatment was not sufficient to describe them because CH3O2 was formed as one of the products in the major channel of reaction (2). This species also reacts with NO3 regenerating CH3O. Use of a numerical model to correct for this regeneration process allowed rate parameters of k1 = (3.5 +/- 1.0) X 10(-11) cm3 molecule-1 s-1 and k2 = (2.3 +/- 0.7) X 10(-12) cm3 molecule-1 s-1 to be determined at 2.4 Torr. There is no pressure dependence observed for reaction (1) between 1 and 2.4 Torr, but the possibility of a slight pressure dependence for reaction (2) exists. These pressure effects are examined using the semi-empirical quantum RRK method.