Vibrational mode-specific quasi-classical trajectory studies for the two-channel HI + C 2 H 5 reaction

• Published in: Physical chemistry chemical physics : PCCP 2023-04, Vol.25 (14), p.9944-9951
• Main Authors: Yin, Cangtao, Czakó, Gábor
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/d2cp05993b

We report a detailed dynamics study on the mode-specificity of the HI + C H two-channel reaction (H-abstraction and I-abstraction), through performing quasi-classical trajectory computations on a recently developed high-level full-dimensional spin-orbit-corrected potential energy surface, by exciting four different vibrational modes of reactants at five collision energies. The effect of the normal-mode excitations on the reactivity, the mechanism, and the post-reaction energy flow is investigated. Both reaction pathways are intensely promoted when the HI-stretching mode is excited while the excitations imposed on C H somewhat surprisingly inhibit the dominant H-abstraction reaction pathway. The enhancement effect of the excitation in the HI vibrational mode is found to be much more effective than increasing the translational energy, similar to the HBr + C H reaction. Not like the Br-abstraction pathway, however, the I-abstraction reaction pathway could be comparable to the dominant H-abstraction reaction pathway. The dominance of the direct stripping mechanism is indicated in H-abstraction while the direct rebound mechanism is observed in I-abstraction. The H-abstraction is much pickier about the initial attack angle distributions for HI than I-abstraction is, which leads to a decrease in reactivity in the H-abstraction reaction pathway. The dominance of side-on CH CH attack in I-abstraction is more obvious than in the case of H-abstraction. In the case of the H-abstraction reaction pathway, the major part of the initial translational energy ends up in translational recoil, while for I-abstraction most energy excites the product C H I.