An eight-degree-of-freedom quantum dynamics study of the isotopic effect on the reaction: HD+C(2)H.

An eight-dimensional time-dependent quantum dynamics calculation is reported to study the isotopic reaction, HD+C(2)H, on a new modified potential energy surface. Initial-state-selected reaction probability, integral cross section, and rate constants are presented in this isotopic reaction study. Initial-state-selected reaction probability is obtained by summing over all the possible product's arrangements in this isotopic reaction study. This study shows that vibrational excitations of HD enhance the reactivity, whereas stretching excitations of C(2)H only have a small effect on the reactivity. Furthermore, the bending excitations of C(2)H, compared to the ground-state reaction probability, hinder the reactivity. The present results are consistent with those obtained for the H(2)+C(2)H reaction. The comparison of these two reactions also shows the isotopic effect in the initial-state-selected reaction probability, integral cross section, and rate constants. The rate constant comparison shows that the HD+C(2)H reaction has a smaller reactivity than the H(2)+C(2)H reaction.