Fermi resonance controlled product branching in the H + HOD reaction

Accurate full-dimensional quantum state-to-state reaction probabilities and integral cross sections are calculated for the title reaction. Product vibrational state distributions are studied for the HOD reactant in various vibrational states. The correlation of initial reactant vibrational excitation with product channel branching and product vibrational state distribution is analyzed in detail. In particular, the effect of bending vibrational excitation on the reactivity is studied. While results for the HOD reactant in the fundamentally excited bending vibrational state confirm intuitive expectation with minor enhancement for both product channels, a surprising effect is found for HOD in the first overtone of bending vibration. Here, the reactivity towards breaking the OD bond is significantly enhanced. This finding can be explained by the state-mixing caused by a 1 : 2 Fermi resonance between the fundamental OD stretch and the first overtone of the bend. The results highlight the importance of a proper analysis of the initial vibrational state.