Origin of the Long Wavelength Fluorescence Band in Some Preparations of J-Aggregates:  Low-Temperature Fluorescence and Hole Burning Study

A broad fluorescence band red-shifted from the absorption line of J-aggregate of pseudoisocyanine chloride in thin films of poly(vinyl sulfate) has been investigated. The fluorescence originates from traps populated by energy transfer from the excitonic band of the J-aggregate. The shift of the fluorescence maxima and the decrease of its intensity with increasing temperature have been explained by interaction of the trap with a 39 cm^-1 phonon mode. Spectral hole burning study shows that the traps are functionally associated with the whole J-aggregate fiber rather than with individual coherently coupled segments of the aggregate.