Four-dimensional quantum mechanical treatment of penta-atomic systems: Case H-2+C2H -> H+C2H2; total reactive probabilities, cross sections, and rateconstants

An advanced quantum mechanical model for the treatment of the dynamics of a diatom-triatom molecule system is presented here. The model has been appli ed to the study of the reactive process H-2+C2H --> H+C2H2, using a four-di mensional (4-D) infinite-order sudden approximation scheme when seven of ni ne degrees of freedom are explicitly considered (the two others are being r educed by means of an averaging of the potential energy surface around the out-of-plane angles). Using a previously reported surface for this reaction [J. Chem. Phys. 101, 8646 (1994)] computations have been carried out to ob tain total reactive probabilities, cross sections, and rate constants. A va lue of 2.68x10(-13) cm(3) molecule(-1) s(-1) was determined for the thermal rate constant at room temperature, in good agreement with the above refere nced theoretical calculation as well as with available experimental data. ( C) 2000 American Institute of Physics. [S0021-9606(00)01524-5].