Quantum dynamics study on the product branching for the C(3P)+C2H2 reaction:: cyclic-C3H versus linear-C3H

Reduced-dimensionality quantum reactive scattering calculations for the C(P-3) + C2H2 reaction have been carried out in order to understand the product branching dynamics Of cyclic-C3H + H and linear-C3H + H. Out-model treats only two degrees of freedom but can explicitly describe both of the C3H isomer product channels. The lowest triplet potential energy surface has been obtained by the hybrid density-functional method at the B3LYP/6-31G(d,p) level of theory. The calculated reaction probabilities were found to be dominated by resonance consistent with the complex-formation potential, and the results show that cyclic-C3H is preferentially formed via the cyclic-C3H2 intermediate produced by insertion Of C(P-3) into the CC bond. We have found that the isomerization from the cyclic-C3H2 to linear-C3H2 intermediate is suppressed by a barrier separating potential wells corresponding to these two intermediates. It has also been found that the energy dependence of the calculated total reaction cross section is in good agreement with the result of crossed molecular beam experiments.