RELAXATION OF INHOMOGENEOUS SPECTRAL BAND-WIDTH OF DYE MOLECULES IN POLAR-SOLVENTS STUDIED BY TIME-RESOLVED HOLE AND FLUORESCENCE SPECTROSCOPY

The comparative studies for time-resolved ground state hole spectra an d time-resolved fluorescence spectra of dye molecules in polar solvent s have been investigated. A marked difference has been shown clearly i n the relaxation times between that are observed from the spectral ban d width, the solvent fluctuation around average energy, and that from the lime resolved peak shift, the average of the solute-solvent intera ction energy. The time correlation function of the solvent relaxation observed from the spectral band width was much slower than that from t he time dependent peak shift in a fluid solvent at higher temperature, but they became comparable at lower temperature. Some possible mechan isms are discussed for understanding of the time dependences of the be havior. At room temperature, due to the relative preponderance of the rotational diffusion over the translational diffusion of solvent molec ules, the energy relaxation takes precedence over the relaxation of th e orientational distribution. It is emphasized that the relaxational m echanism presented here is applicable for both the time-resolved fluor escence and the ground state hole spectra.