Quantum dynamics study of vibrational excitation effects and energy requirement on reactivity for the O + CD4/CHD3 → OD/OH + CD3 reactions.

A quantum reactive dynamics, six-degrees-of-freedom, time-dependent wave packet method is employed to study vibrational enhancement and energy requirement on reactivity of the O((3)P) + CD4/CHD3 → OD/OH + CD3 reactions. The calculations show, for O + CD4, that all the vibrational excitations of CD4 enhance reactivity, which agrees with quasi-classical trajectory results. However, this finding contradicts the experimental observation where the bending excitation suppresses reactivity. The present study also reveals that translational energy, in general, is more effective to enhance reactivity than vibrational energy; however, at higher collision energy, vibrational energy is slightly more effective than translational energy. For O + CHD3, the stretching and bending excitations of CHD3 enhance the reaction, whereas the umbrella motion hinders reactivity. The calculated excitation functions agree well with experiments.