Theoretical study of photoinduced proton coupled electron transfer reaction using the non-perturbative hierarchical equations of motion method

Abstract

Photoinduced proton coupled electron transfer (PCET) reactions, in which the charge transfer process is initiated by light absorption, are of special interest to both theoretical and experimental studies. In this work, by employing the non-perturbative hierarchical equation of motion method, we investigate several aspects of concerted photoinduced PCET based on an extended spin-boson model where the correlation between the electron and proton baths is considered explicitly. It is found that the vibrational relaxation on the donor state plays an important role in the initial stage of the non-equilibrium PCET dynamics after photon excitation, and the equilibrium rate dynamics is recovered at times longer than the vibrational relaxation time scale. The numerically exact results are compared with those obtained from the non-equilibrium Fermi’s golden rule, which is found to be less accurate for the non-equilibrium dynamics in the case of large electronic couplings. The isotope effect in photoinduced PCET is also investigated, where the non-equilibrium dynamics and equilibrium rate dynamics show very different isotope effects.