Effects of strong excitation induced disorder on pump–probe spectra of molecular aggregates

We have studied the effects of induced off-diagonal disorder on pump–probe spectra in J-aggregates. Changes of the disorder, i.e. randomness in excite energy of site molecules and inter-molecular coupling within a 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. The possibility of the transient stage of aggregate ensembles exhibiting lasing due to the excess off-diagonal disorder is demonstrated.