A comparison study of the H + CH4 and H + SiH4 reactions with eight-dimensional quantum dynamics: normal mode versus local mode in the reactant molecule vibration

摘要

While molecular vibration of CH4 is well described by the normal-mode paradigm, the local mode picture is more suitable for understanding the SiH4 stretching vibrational motion. To compare the roles of the two types of molecular vibration in reaction dynamics, the H + CH4 ->H2 + CH3 and H + SiH4 ->H2 + SiH3 reactions have been investigated using an eight-dimensional (8D) quantum dynamics method in which the nonreact-ing XH3 (X = C, Si) group keeps its C_(3v) symmetry in the reaction. The reaction probabilities, integral cross sections and thermal rate constants in the temperature range of 200-2,000 K were calculated for both reactions. Strong mode specificity was found in both reactions, and the differences were rationalized by the vibrational characteristics of the CH4 and SiH4 reactants.