An eight-degree-of-freedom quantum dynamics study for the H2+C2H system

An eight-degree-of-freedom (8DOF) time-dependent wave-packet approach has been developed to study the H(2)+C(2)H-->H+C(2)H(2) reaction system. The 8DOF model is obtained by fixing one of the Jacobi torsion angle in the nine-degree-of-freedom AB+CDE reaction system. This study is an extension of the previous seven-degree-of-freedom (7DOF) computation [J. Chem. Phys. 119, 12057 (2003)] of this reaction system. This study shows that vibrational excitations of H(2) enhance the reaction probability, whereas the stretching vibrational excitations of C(2)H have only a small effect on the reactivity. Furthermore, the bending excitation of C(2)H, compared to the ground-state reaction probability, hinders the reactivity. A comparison of the rate constant between the 7DOF calculation and the present 8DOF results has been made. The theoretical and experimental results agree with each other very well when the present 8DOF results are adjusted to account for the lower transition state barrier heights found in recent ab initio calculations.