Vibrational mode specificity in H + NHD2 → H2 + ND2: A full-dimensional quantum dynamics study.

The vibrational mode specificity in the polyatomic reaction H + NHD2 → H2 + ND2 is investigated using full-dimensional quantum dynamics calculations. Using a mixed Jacobi/Radau coordinate system, we perform time-dependent wave packet calculations to explore how different vibrational excitations of the NHD2 reactant influence reaction probabilities and integral cross sections. This study reveals that specific vibrational modes, particularly the umbrella mode and the N-H stretching mode, significantly enhance reactivity by directly coupling with the reaction coordinate. In contrast, vibrational excitations localized on the non-reactive ND2 group exert minimal effects. Notably, the umbrella mode's tunneling splitting leads to distinct dynamics for its two components, with higher excitation states showing complex energy-dependent behavior. These findings highlight the critical role of mode-specific vibrational excitations in polyatomic reaction dynamics and underscore the necessity of accurate full-dimensional quantum calculations for elucidating complex reaction mechanisms.