Mode-specific quantum dynamics and kinetics of the hydrogen abstraction reaction OH + H2O → H2O + OH.

Abstract

Hydrogen abstraction processes are prevalent in a wide range of chemically active environments. In this work, the prototypical hydrogen exchange reaction OH + H2O → H2O + OH is investigated on an accurate ab initio based potential energy surface using an initial state-selected time-dependent wave packet method. Exciting either the symmetric stretching mode or the antisymmetric stretching mode of the reactant H2O promotes the reaction more than exciting the bending mode. The vibrational energy initially deposited in H2O is more efficient than the translational energy in promoting the reaction. There exists a remarkable synergistic effect between the stretching mode and the bending mode as the efficacy for the combination band excitation is larger than the sum of individual excitations. The mode-specific dynamics is partially rationalized by the sudden vector projection model. Besides, the mode-specific rate constants apparently exhibit a strong non-Arrhenius behavior at low and moderate temperatures.