The theoretical basis of Arrhenius rate law which is the paradigm of thermally activated processes, in general, rests on equilibrium statistical mechanics and more generally on non-equilibrium stochastic processes. Here we present a study of quantum dynamical generalization of the expression for rate coefficient in the context of quantum non-equilibrium processes in condensed media. Brownian motion lies at the heart of activated rate processes and quantum Brownian motion as compared to its classical counterpart rests on a technically different footing. Here we develop a scheme that leads to a...