Experimental and theoretical study of the recombination reaction CH 3+CH 3→C 2H 6

Abstract

New measurements at 200 K, 300 K and 408 K are reported for the rate constant for the self-recombination of methyl radicals in Ar buffer gas. The 200 K measurements were made using laser flash photolysis while the 300 K and 408 K measurements were carried out at low pressures in a flow reactor. A variational RRKM calculation was performed to represent these new measurements and those previously published. The comparison between theory and experiment supports both a negative temperature dependence to the high pressure limit of recombination and a substantial positive temperature dependence to 〈ΔE〉tot, the average energy transferred in an Ar−C2H6* collision. An analytic representation of the recombination rate constant valid for all pressures where the rate constant exceeds 10−12 cm3/molecule-sec is determined over the temperature range of 200 K to 2000 K.