LATTICE-DYNAMICS IN DISORDERED MATERIALS PROBED THROUGH OPTICAL-RESPONSES

From the resonance fluorescence spectra measured for dye molecules in organic molecular glasses at low temperatures, we determined the densi ty of states of vibrational host modes weighted by the electron-phonon coupling strength for each sample. The normalized shape of this weigh ted density of states was found to exhibit the quantitatively universa l feature which coincides with that obtained for dye-doped organic and inorganic amorphous polymers, though the nature of disorder is widely varied among the materials. Raman scattering spectra were also measur ed for host glasses at low temperatures. Although the same kind of mat erials showed similar spectral shapes, remarkable difference was found among the groups of materials. These results indicate crucial importa nce of classifying types of vibrational modes in order to clarify the low-frequency dynamics of disordered materials, which will be discusse d taking account of recent studies in the literature. (C) 1998 Elsevie r Science B.V. All rights reserved.