Reabsorption and High Density Excitation Effects on the Time-Resolved Fluorescence Spectra of Anthracene Crystal

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Abstract
The spectral dependence of fluorescence lifetime and the time-resolved fluorescence spectra at high and low density excitations were measured for pure anthracene crystals. A nitrogen gas laser was used as excitation source. The fluorescence lifetime with low density excitation was found to be shorter in the shorter wavelength region than in the longer wavelength region and to be longer over whole wavelength region for the thick crystal than for the thin crystals or powders. This can be explained by the reabsorption effect. Furthermore, a fluorescence intensity increment due to high density excitation was found to be more predominant in the shorter wavelength region than in the longer wavelength region. This high density excitation effect is discussed in terms of decreasing reabsorption caused by the ground state depletion.