Ignition induced the short-term action of UV light as possible evidence of chain branching in the reacting CH3Cl + Cl2 mixture

Abstract

Ignition takes place in a mixture of chloromethane and chlorine at atmospheric pressure and room temperature 0.1 s after the irradiation of the mixture with a UV light pulse from a mercury quartz lamp. Temperature fields are presented, which demonstrate the development of the ignition process in the dark period. Calculations show that, after the initiation is stopped, the concentration of chlorine atoms decreases to a critical value within a time of the order of 0.02 s. The observed ignition can be explained by chains branching caused by the decay of the excited CCl₃^* radical that have accumulated energy upon the successive substitution of chlorine atoms for hydrogen in the chloromethane molecule.