Shortcomings of current theories of non-Markovian activated rate processes

We calculate the barrier crossing rate constants for a Brownian particle in a double well potential experiencing a non-Markovian friction kernel using full stochastic simulation. We compare the simulation results with recently proposed interpolation formulas which are based on the Grote–Hynes relation and energy diffusion mechanism. We find that such formulas fail in the intermediate regime by orders of magnitude. Therefore we question interpretations of dependence of isomerization rate data on the viscosity based on such ideas.