RECOMBINATION OF RADICALS IN THE HIGH-PRESSURE AND HIGH-TEMPERATURE LIMIT - PART 2 - REACTION CH3+H

The reaction CH3 + H is examined theoretically at high pressures and t emperatures (T > 200 K) on the basis of adiabatic curves that describe weak, long-range interactions between reactants. These curves are obt ained by using available ab initio results and by solving the pertinen t Schrodinger equation. A mechanism of radical recombination involves the formation of weakly bound CH3...H intermediates which can be forme d provided that the orbital momentum of the system does not exceed a t hreshold value of [l(lim)] = 13 +/- 1. The rate constant for recombina tion exhibits a very weak negative temperature dependence and is under estimated compared with experiment. The contribution of direct recombi nation involving a strongly bound complex depends on temperature. At h igher temperatures it may exceed 50%.