Electron transfer from the perspective of electron transmission: Biased non-adiabatic intermolecular reactions in the single-particle picture.

In this work, we revisit Hopfield's formulation of non-adiabatic electron transfer between uncorrelated redox species within the single-particle picture description of electron transmission commonly applied in solid-state systems. The formulation is applied to a model system, similar to that often found in solid-state electron tunneling studies, consisting of redox species separated by an insulating tunneling barrier. Redox tunneling across such an insulator is predicted to demonstrate a marked asymmetry, ranging from one to three orders of magnitude between forward and reverse bias electron transfer rates, when reactants possess dissimilar reorganization energies. This significant asymmetry is shown to arise from trapezoidal reshaping of the integrated Gamow tunneling barrier and corresponding transmission probability under an applied bias. In general, this work aims to further bridge concepts between the electron transfer and transport communities.