Quasi-Classical Trajectory Calculations Analyzing the Dynamics of the C-H Stretch Mode Excitation in the H + CHD_3 Reaction

摘要

A state-to-state dynamics study was performed at a collision energy of 1.53 eV to analyze the effect of the C-H stretch mode excitation on the dynamics of the gas-phase H + CHD_3 reaction, which can evolve along two channels, H-abstraction, CD_3 + H_2, and D-abstraction, CHD_2 + HD. Quasi-classical trajectory calculations were performed on an analytical potential energy surface constructed previously by our group. First, strong coupling between different vibrational modes in the entry channel was observed; i.e., the reaction is non-adiabatic. Second, we found that the C-H stretch mode excitation has little influence on the product rotational distributions for both channels, and on the vibrational distribution for the CD_3 + H_2 channel. However, it has significant influence on the product vibrational distribution for the CHD_2 + HD channel, where the C-H stretch excitation is maintained in the products, i.e., the reaction shows mode selectivity, reproducing the experimental evidence. Third, the C-H stretch excitation by one quantum increases the reactivity of the vibrational ground-state, in agreement with experiment. Fourth, the state-to-state angular distributions of the CD_3 and CHD_2 products are reported, finding that for the reactant ground-state the products are practically sideways, whereas the C-H excitation yields a more forward scattering.