TRANSFER AND DECAY OF AN EXCITON COUPLED TO VIBRATIONS IN A DIMER

Transfer and decay dynamics of an exciton coupled to a polarization vi bration in a dimer is investigated in a mixed quantum-classical pictur e with the exciton decay incorporated by a sink site. Using a separati on of time scales, it is possible to explain analytically the most imp ortant characteristics of the model. If the vibronic subsystem is fast , these are the enhancement of nonlinear self-trapping due to the sink and the slowing down of the exciton decay for large coupling or sink strength. Numerical results obtained recently for the discrete self-tr apping (DST) approximation to the model are quantitatively explained a nd dynamic effects beyond this approximation are found. If the vibroni c subsystem is slow, the behavior of the system follows closely the pr edictions of the adiabatic approximation. In this regime, the exciton decay crucially depends on the initial conditions of the vibronic subs ystem. In the transition regime between the adiabatic and DST approxim ation, complex dynamics is observed by numerical computation. We discu ss the correspondence to the chaotic behavior of the excitonic-vibroni c coupled dimer without trap.