Probing photoinduced proton coupled electron transfer process by means of two-dimensional electronic-vibrational spectroscopy.

We develop a detailed theoretical model of photo-induced proton-coupled electron transfer (PPCET) processes, which are at the basis of solar energy harvesting in biological systems and photovoltaic materials. Our model enables to analyze the dynamics and the efficiency of a PPCET reaction under the influence of a thermal environment by disentangling the contribution of the fundamental electron transfer (ET) and proton transfer (PT) steps. In order to study quantum dynamics of the PPCET process under an interaction with non-Markovian environment we employ the hierarchical equations of motion (HEOM). We calculate transient absorption spectroscopy (TAS) and two-dimensional electronic-vibrational spectroscopy (2DEVS) signals in order to study the nonequilibrium reaction dynamics. Our results show that different transition pathways can be separated by TAS and 2DEVS.