Kinetics of the Reaction of CH3O2 + NO: A Temperature and Pressure Dependence Study with Chemical Ionization Mass Spectrometry

Abstract

The overall rate coefficient (k4) for the reaction CH3O2 + NO → products (4) has been measured by using the turbulent flow technique with chemical ionization mass spectrometry (CIMS) for the detection of reactants and products. The temperature dependence of the rate coefficient was investigated between 193 and 300 K. Across the temperature range the experimentally determined rate coefficients were fitted by using an Arrhenius type analysis to yield the expression k4 = ( ) × 10-12 exp[(435 ± 35)/T] cm3 molecule-1 s-1. Experiments were carried out at 100 and 200 Torr total pressure within the stated temperature range, where the rate coefficients were shown to be invariant with pressure. The branching ratio of the reaction was also assessed as a function of temperature and was found to proceed 100 ± 10% via the channel forming CH3O + NO2, there being no discernible increase in the yield of CH3ONO2 at low temperatures. This work represents the first study of the branching ratio as a function of temperature an...