Towards AN Understanding of Nonlinear Solvent Effects in Condensed Phase Activated Rate Processes.

Solvation effects on the reaction potential and activated barrier crossing rate are considered for classical condensed phase (multi-dimensional) systems exhibiting nonlinear solute reaction potentials and nonlinear solute -solvent couplings. An analytic theory is developed for the activated barrier crossing rate constant in condensed phase systems exhibiting time and space dependent solvent generated friction on the reaction coordinate. Predictions of this theory are compared to results of numerically exact generalized Langevin equation simulations for model systems. The relationship of the gas phase (one-dimensional) reaction potential to the condensed phase potential of mean force is also derived in terms of the initial magnitude of the time dependent solvent friction. Implications for the reaction coordinate dependence of the solvent friction and the analysis of experimental results are then discussed. The Feynman path integral formulation of quantum transition state theory is also extended to treat the case of nonlinear solute-solvent couplings. The quantum barrier crossing rate is examined for a nonlinear system by path integral Monte Carlo simulations.