Quantum Dynamics Study of OH^-+CH₃I Reaction: Reaction Probability, Integral Cross Section, and Energy Efficacy

We investigate the reaction probability, integral cross section, and energy efficiency of the OH^-+CH₃I reaction using the time-dependent quantum dynamics wave packet method. A four-degree-of-freedom dynamics model is developed for this study due to the synchronized S_N2 bond-breaking and formation mechanism. We find that the reaction probability decreases as a function of the collision energy, which is a typical character of reactions with a negative energy barrier. The ground-state integral cross section calculated using this model is in excellent agreement with the quasi-classical trajectory results. The integral cross-section ratios of the vibrational excitations over the ground state, at the same equal amount of total energy, indicate that the vibrational motion of the CH₃-I is more efficient in enhancing the reactivity than the translational motion, which, in turn, has a bigger contribution to the reactivity than the C-H₃ vibrational motion. The energy efficacy order in the reactivity is confirmed by the sudden vector model prediction.