Singlet Exciton Annihilation in the Picosecond Fluorescence Decay of 1,1'-Diethyl-2,2'-Cyanine Chloride Dye J-Aggregate

We present a new study which reveals a strong dependence on excitation intensity in the time-resolved fluorescence decay of the J-aggregate of the title dye. Strong intermolecular interaction in the J-aggregate is indicated by the large red shift (1700 cm−1) and band narrowing (1475 to 125 cm−1) in the absorption spectrum compared with unassociated dye molecules in solution. Exciton dynamics in the J-aggregate are interesting because of the lower dimensionality and stronger intermolecular interaction compared to other molecular crystals and because of the photographic spectral sensitization properties of the J-aggregate.