Nonadiabatic quantum dynamics of C(1D)+H2 → CH+H: Coupled-channel calculations including Renner-Teller and Coriolis terms

The Renner-Teller (RT) coupled-channel dynamics for the C(D-1) + H-2(X-1 Sigma(+)(g)) -> CH(X-2 Pi) + H(S-2) reaction has been investigated for the first time, considering the first two singlet states (a) over tilde (1)A' and (b) over tilde (1)A '' of CH2 dissociating into the products and RT couplings, evaluated through the ab initio matrix elements of the electronic angular momentum. We have obtained initial-state-resolved probabilities, cross sections and thermal rate constants via the real wavepacket method for both coupled electronic states. In contrast to the N(D-2) + H-2(X-1 Sigma(+)(g)) system, RT effects tend to reduce probabilities, cross sections, and rate constants in the low energy range compared to Born-Oppenheimer (BO) ones, due to the presence of a repulsive RT barrier in the effective potentials and to long-lived resonances. Furthermore, contrary to BO results, the rate constants have a positive temperature dependence in the 100-400 K range. The two-state RT rate constant at 300 K, lower than the BO one, remains inside the error bars of the experimental value. (C) 2011 American Institute of Physics. [doi:10.1063/1.3636083]