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Here, an initial state selected time-dependent wave packet method is applied to study the dynamics of the OH + CHD₃ reaction with a six-dimensional model on a newly developed full-dimensional ab initio potential energy surface (PES). This quantum dynamical (QD) study is complemented by fulldimensional quasi-classical trajectory (QCT) calculations on the same PES. The QD results indicate that both translational energy and the excitation of the CH stretching mode significantly promote the reaction while the excitation of the umbrella mode has a negligible effect on the reactivity. For this early barrier reaction, interestingly, the CH stretching mode is more effectivemore » than translational energy in promoting the reaction except at very low collision energies. These QD observations are supported by QCT results. The higher efficacy of the CH stretching model in promoting this early barrier reaction is inconsistent with the prediction of the naively extended Polanyi’s rules, but can be rationalized by the recently proposed sudden vector projection model.« less

In this work, an eight-dimensional quantum dynamical model is proposed and applied to the title reaction. The reaction probabilities and integral cross sections have been determined for both the ground and excited vibrational states of the two reactants. The results indicate that the H₂ stretching and CH₃ umbrella modes, along with the translational energy, strongly promote the reactivity, while the CH₃ symmetric stretching mode has a negligible effect. The observed mode specificity is confirmed by full-dimensional quasi-classical trajectory calculations. Lastly, the mode specificity can be interpreted by the recently proposed sudden vector projection model, which attributes the enhancement effects ofmore » the reactant modes to their strong couplings with the reaction coordinate at the transition state.« less