Disentangling the complexity of coupled vibrations by two-dimensional electronic-vibrational spectroscopy

We employ two-dimensional electronic-vibrational (2DEV) spectroscopy to study the coherent dynamics of coupled vibrational modes in an excitonically-coupled dimer model. The advantage of separating excitation and detection in different frequency regimes allows us to directly probe the electronic and vibrational coherences in the time-evolved 2DEV spectra. The complexity of vibrational coherence of two coupled modes is directly revealed by cross peaks in the 2DEV spectra. With the help of the ensuing time traces, we can follow how the vibrational coherence changes over time in the monomer model and, subsequently, in the dimer model. We show that the complexity of two coupled vibrational modes and the interaction between electronic and vibrational coherences in molecular systems can be effectively disentangled using the 2DEV spectroscopy technique.