Quantum Wave Packet Studies of the C(1D) + H2 → CH + H Reaction: Integral Cross Section and Rate Constant

Abstract

Using a Chebyshev wave packet method, the initial state-specified (vi = 0, ji = 0) integral cross section and rate constant are obtained for the title reaction on the latest version of the ab initio potential energy surface. All partial wave contributions up to J = 47 are calculated explicitly within the coupled states (CS) approximation. The resulting integral reaction cross section in the collision-energy range of 0.0−0.5 eV displays an oscillatory structure due to numerous long-lived resonances supported by the deep CH2 well. The rate constant up to 800 K is nearly temperature-independent except for an initial rise below 100 K. The calculated rate constant at room temperature is in reasonably good agreement with the latest experimental measurement. In addition, exact calculations including the Coriolis coupling have been carried out for three selected partial waves, J = 2, 4, and 10. In these Coriolis-coupled calculations, a more accurate and efficient scheme is proposed that allows for a significant reduction of the grid size as well as the spectral range. Comparison with the corresponding CS results indicates that the neglect of the Coriolis coupling leads to the underestimation of the cross section and the rate constant.