Unimolecular reaction rate theory for transition states of any looseness. 3. Application to methyl radical recombination

Abstract

The theory for unimolecular reactions described in part 1 is applied to the recombination of methyl radicals in the high-pressure limit. The model potential energy surface and the methodology are briefly described. Results are presented for the recombination rate constant k_ ∞ at T = 300, 500, 1000, and 2000 K. Canonical and Boltzmann averaged microcanonical values of k_ ∞ are compared, and the influence of a potential energy interpolation parameter and a separation-dependent symmetry correction on k_ ∞ are examined. Earlier theoretical models and extensive experimental results are compared with the present results which are found to have a negative temperature dependence. The present results agree well with some of the available but presently incomplete experimental determinations of the high-pressure recombination rate constant for this reaction over the 300-2000 K temperature range. There is also agreement with a decomposition rate constant for a vibrationally excited ethane molecule produced by chemical activation.

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