Dynamical effects from resonance Raman and fluorescence studies of the molecular exciton system perylene

The resonance Raman profiles were measured for a perylene crystal exciton state (Au) corresponding to the 0–0 transition of the molecular 1B2u(S1) state. At both 77 and 4.2 °K the profiles of these extremely thin crystals do not coincide with the absorption spectra. This effect is frequency dependent damping perhaps caused by exciton–phonon interactions. The efficiency of resonant scattering relative to excimer emission is used to measure an exciton dephasing time of 6.4×10−14 sec. The luminescence of the population resulting from this loss of coherence was not observed suggesting that these excitons disappear within 5×10−13 sec.