Recombination of radicals in the high-pressure and high-temperature limit Part 2Reaction CH3+H

Abstract

The reaction CH₃+H is examined theoretically at high pressures and temperatures (T>200 K) on the basis of adiabatic curves that describe weak, long-range interactions between reactants. These curves are obtained by using available abinitio results and by solving the pertinent Schrödinger equation. A mechanism of radical recombination involves the formation of weakly bound CH₃···H intermediates which can be formed provided that the orbital momentum of the system does not exceed a threshold value of 〈l_lim〉=13±1. The rate constant for recombination exhibits a very weak negative temperature dependence and is underestimated compared with experiment. The contribution of direct recombination involving a strongly bound complex depends on temperature. At higher temperatures it may exceed 50%.