Electron transfer rates for asymmetric reactions

We use a numerically exact real-time path integral Monte Carlo scheme to compute electron transfer dynamics between two redox sites within a spin-boson approach. The case of asymmetric reactions is studied in detail in the least understood crossover region between nonadiabatic and adiabatic electron transfer. At intermediate-to-high temperature, we find good agreement with standard Marcus theory, provided dynamical recrossing effects are captured. The agreement with our data is practically perfect when temperature renormalization is allowed. At low temperature we find peculiar electron transfer kinetics in strongly asymmetric systems, characterized by rapid transient dynamics and backflow to the donor.