Abstract
Decay curves and spectral shapes of the singlet-exciton luminescence in anthracene crystals have been studied at room temperature and found to depend on the experimental geometry and on the penetration depth of the exciting light. The well-known wavelength-dependent decay time and time-dependent spectrum occur only when the luminescence is excited in the process of the one-photon absorption and is observed in the backward-scattering geometry. In the forward-scattering geometry, the decay time is independent of the luminescence wavelength. When the excitons are uniformly generated in the crystal in the process of the two-photon absorption, the wavelength-dependent decay time and time-dependent spectrum do not occur even in the backward-scattering geometry. These results are interpreted in terms of diffusion of the singlet excitons and reabsorption of the short wavelength photons of the exciton luminescence.
Published Version
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