Disordering induced emission of strongly excited molecular aggregates

Abstract

This paper investigates transient effects of disordering induced changes of the spectra in strongly excited one-dimensional aggregates by short light pulses. Exciton-exciton annihilation and subsequent excess energy degradation over the aggregate is accounted for as a source of the additional static and dynamic disordering. Randomness in excite energy of site molecules and inter-molecular coupling within meso-aggregates is considered by introducing different random Hamiltonian matrices for two ensembles of aggregates. The theory allows to interpret the intensity-dependent spectra on the J-aggregates as contributed from the combined action of exciton-exciton annihilation and subsequent dynamic disordering processes. Specifically, the rise of the off-diagonal disorder after strong excitation and subsequent energy degradation processes in molecular aggregate produces a blue shift of the pump probe spectra. Moreover, this work have studied conditions under which the sign of the strongly excited aggregate changes, because change in sign of the spectra hints for the appearance of the emissive properties in the system.