Studies on atom–triatom reactive scattering. Classical dynamics of H + C2H collisions

Abstract

The classical dynamics of the collisions of hydrogen atoms with C₂H has been studied using a six-dimensional potential-energy surface for the ground state of C₂H₂. At low collision energies complexes are formed which have predominantly acetylene rather than vinylidene geometries. The estimated rate constant for this recombination reaction is 100 times larger than a published value determined by transition-state theory.

At high energies the endothermic reaction to C₂+ H₂ is possible. It has been found that vibrational energy is more efficient than translational energy in promoting this reaction. Moreover higher reactivity is obtained by exciting initially the CH normal mode than the CC mode. Excitation to a state in which both the bending mode and CC stretching mode were excited gave a low reactivity even though the classical motion in this state was stochastic.