Quantum rate dynamics for proton transfer reaction in a model system: effect of the rate promoting vibrational mode.

We extended our previous calculation of the quantum rate dynamics for a model system of proton transfer (PT) reaction using the Liouville space hierarchical equations of motion method in this study. A rate promoting vibrational (RPV) mode that symmetrically coupled to the proton coordinate was included in the quantum dynamics calculations, in order to study the effect of enhanced tunneling by the proton donor-acceptor motion. Adding the RPV mode is observed to increase the PT rate and reduce the kinetic isotope effects. We also found that the PT dynamics is influenced by the dissipation of the RPV mode. Besides this extension, in the case without the RPV, we investigated whether the PT rate dynamics in the deep tunneling regime can reduce to an effective two-state spin-boson type of model and found that this is only possible at low reorganization energies.