Vibrational mode-specific dynamics of the Cl + CH3CN reaction.

Understanding the vibrational mode-specific dynamics of chemical reactions is crucial for unraveling the fundamental mechanisms that govern reactivity and product formation. In this study, we investigate the Cl + CH3CN reaction using quasi-classical trajectory simulations on a previously developed, high-quality, full-dimensional potential energy surface. By selectively exciting individual vibrational modes of the CH3CN reactant, we systematically analyze their influence on reaction probabilities and cross sections and, in the case of the major H-abstraction channel, on scattering and attack angle distributions, as well as product energy partitioning across a range of collision energies. Furthermore, a vibrational mode-specific product analysis, combined with energy-based Gaussian binning, was conducted to examine how initial mode excitation influences product state distributions. Our results reveal that excitation of specific reactant vibrational modes can enhance the H-abstraction probability without altering the overall reaction mechanism. A significant portion of the initial vibrational energy is transferred to the internal energy of the products, while the collision energy primarily contributes to their translational energy. The CH2CN product exhibits well-defined, mode-specific vibrational excitation patterns, reflecting distinct energy redistribution pathways during the reaction. These findings provide deeper insight into the role of vibrational energy in promoting or altering chemical reaction pathways in a polyatomic system.