Interplay between nonadiabatic dynamics and Frenkel exciton transfer in molecular aggregates: formulation and application to a perylene bismide model.

The quantum dynamics of linear molecular aggregates in the presence of S0 → S1 and S0 → S2 transitions is investigated by putting emphasis on the interplay between local nonadiabatic S2 to S1 deactivation and Frenkel exciton transfer. The theoretical approach combines aspects of the linear vibronic coupling and Frenkel exciton models. Dynamics calculations are performed for the absorption spectrum and the electronic state populations using the multiconfiguration time-dependent Hartree approach. As an application, perylene bisimde J-type dimer and trimer aggregates are considered, including four tuning and one coupling mode per monomer. This leads to a dynamical model comprising up to 7 electronic states and 15 vibrational modes. The unknown nonadiabatic coupling strength is treated as a parameter that is chosen in accordance with available absorption spectra. This leaves some flexibility that can be limited by the clearly distinguishable population dynamics.