Distinctive character of electronic and vibrational coherences in disordered molecular aggregates

Coherent dynamics of coupled molecules are effectively characterized by the two-dimensional electronic spectroscopy. Depending on the coupling between electronic and vibrational states, oscillating signals of purely electronic, purely vibrational or mixed character are observed with the help of oscillation maps, constructed from time-resolved spectra. Amplitude of beatings caused by electronic coherences is heavily affected by energetic disorder and consequently electronic coherences are quickly dephased. Beatings with vibrational character weakly depend on the disorder, ensuring their long-time survival. We show that detailed modeling of two-dimensional spectroscopy signals of molecular aggregates provides direct information on the origin of the coherent beatings.