Comprehensive Investigations of the Cl

Cl+CH3OH -> HCl+CH3O/CH2OH is a prototypical multiple-channel reaction. Experimentally, ample dynamical and kinetic information is available, but there are still many uncertainties concerning the reaction mechanism. Theoretical investigations are rare due to the absence of a potential energy surface (PES), which has greatly hindered our understanding of the reaction dynamics. Using a machine-learning approach, an accurate full-dimensional PES for the title reaction based on tens of thousands of high-level ab initio data is reported. Comprehensive dynamical calculations were performed on the PES using quasi-classical trajectories, and the results provide insights into the reaction kinetics and dynamics. The calculated non-Arrhenius rate coefficients are consistent with the experimental data, attributable to a complex-forming mechanism at low temperatures. At high energies, the reaction is dominated by a direct mechanism, which results in dominant forward scattering via a stripping mechanism augmented by less prominent sideways and backward scattering via a rebound mechanism. At collision energies of 5.6 and 8.7 kcal/mol, the measured product translational energy and ro-vibrational state distributions of HCl are well reproduced. In addition, mode specificity is revealed and rationalized by the sudden vector projection model. This work sheds valuable light on the microscopic mechanism and dynamics of this prototypical multichannel reaction.