Michael J. Pilling

The testing of models for unimolecular decomposition via inverse Laplace transformation of experimental recombination rate data

Abstract The inversion of experimental temperature-dependent recombination rate data, to obtain microcanonical rate constants, is discussed and applied to methyl radical recombination. It is demonstrated that inverse Laplace transformation provides an efficient means of comparing experimental data with model calculations.

Experimental and Theoretical Study of the Recombination Reaction CH3 + CH3 > C2H6.

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.