Dependence of the chemical dynamics of intercluster association reactions on the strength of the solute–solvent intermolecular potential

Abstract

Classical trajectory calculations are performed to investigate how microscopic solvation influences the H+CH3→CH4 reaction mechanism, rate constant, energetics, product energy, and angular momentum partitioning; and how these solvation effects depend on the solute–solvent interaction strength. Without solvation, the final energy and rotational angular momentum of CH4 strongly depend on the H+CH3 relative translational energy. However, for HAr2+CH3 with a normal H–Ar Lennard-Jones interaction strength εHAr0, a spectator-stripping mechanism dominates the reactive collisions so that both the final CH4 energy and rotational angular momentum do not significantly depend on the relative translational energy. The association cross section to form CH4 is slightly larger for HAr2+CH3 than for H+CH3. When the H–Ar interaction strength for HAr2 is increased from 1 to 100εHAr0, it is found that (1) the association cross section to form CH4 is insensitive to the H–Ar interaction strength, suggesting a long-range transition state; (2) the reaction mechanism changes from a spectator-stripping model to a complex one, which alters the character of the CH4+Ar2 product energy and angular momentum partitioning; and (3) the formation of the Ar2–CH4 complex leads to stabilized CH4 product, with substantial energy transfer from CH4 for the strongest H–Ar interaction strength of 100εHAr0.