DEPENDENCE OF THE CHEMICAL-DYNAMICS OF INTERCLUSTER ASSOCIATION REACTIONS ON THE STRENGTH OF THE SOLUTE SOLVENT INTERMOLECULAR POTENTIAL

Classical trajectory calculations are performed to investigate how mic roscopic solvation influences the H+CH3-->CH4 reaction mechanism, rate constant, energetics, product energy, and angular momentum partitioni ng; and how these solvation effects depend on the solute-solvent inter action strength. Without solvation, the final energy and rotational an gular momentum of CH4 strongly depend on the H+CH3 relative translatio nal energy. However, for HAr2+CH3 with a normal H-Ar Lennard-Jones int eraction strength epsilon(HAr)0, a spectator-stripping mechanism domin ates the reactive collisions so that both the final CH4 energy and rot ational angular momentum do not significantly depend on the relative t ranslational energy. The association cross section to form CH4 is slig htly larger for HAr2+CH3 than for H+CH3. When the H-Ar interaction str ength for HAr2 is increased from 1 to 100epsilon(HAr)0, it is found th at (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 ener gy 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 100ep silon(HAr)0.