The thermal reactions of CH3

Abstract

The thermal reactions of CH3 radicals have been investigated in reflected shock waves experiments at temperatures between 1224 and 2520 K. The fast dissociation of CH3I served as the source of CH3. Experiments were performed at three loading pressures with variations in [CH3I]0. H atoms, formed in the reaction, 2CH3→C2H5+H, were measured by the atomic resonance absorption spectrometric (ARAS) technique. The product ethyl radicals subsequently decompose to give a second H atom and ethylene. A reaction mechanism was used to fit the, data, and the resulting value for the rate constant was 5.25×10−11 exp(-7384K/T) cm3 molecule−1s−1. This value is compared to earlier determinations. At higher temperatures, 2150–2520 K, the H-atom formation rate was dominated by CH3 thermal dissociation. With simulations, the rate constant for CH3+Kr→CH2+H+Kr could be determined. The rate constant for this process is k=4.68×10−9 exp(-42506 K/T) cm3 molecule−1s−1. This result is compared to earlier experimental determinations and also to theoretical calculations using the semiempirical Troe formalism.