An effective barrier model for describing quantum mechanical activated rate processes in condensed phases

An analytic variational model is developed to treat quantum activated rate processes in condensed phase systems. An effective parabolic barrier curvature in this model describes both the barrier nonlinearity along the reaction coordinate as well as the influence of dissipation from the fluctuating condensed phase environment. The theory is developed by exploiting the relationship between the statistics of Feynman path integral centroid densities and the rate of quantum activated events. The result is numerically tested on a model activated dynamics problem and applied to estimate the quantum tunneling correction to an SN2 reaction in water.