Electron transfer through time-dependent bridges: tunneling by virtual transitions that break the Born–Oppenheimer approximation

For bridge-mediated electron transfer through time-dependent bridges it is shown that the superexchange mechanism may not be the only relevant tunneling mechanism. Electronic tunneling from donor to acceptor could also be mediated by a type of breakdown of the Born–Oppenheimer adiabatic approximation. A time-dependent effective Hamiltonian is derived for this process.