BRILLOUIN SPECTRA IN AMORPHOUS SOLIDS

Abstract

Author Institution: IBM Research Laboratory, San JosePolymeric solids are known to undergo a number of relaxational transitions. These transitions involve either changes in the skeletal and/or side group structure and their determination is strongly dependent on the frequency of the detection method and other extrinsic factors. This report deals with the detection of phase transitions in amorphous solids in the gigahertz range using acoustical phonons as a probe. The relationship of observed phonon velocities and scattering intensities to bulk properties is investigated and in certain cases it has also been possible to establish relaxation times associated with internal degrees of freedom in the sub-skeletal or side chain regions. Main consideration is given to developing a theory which accounts for changes observed in the Landau-Placzek ratio, absorption coefficients, and phonon velocities as temperature and phonon frequencies are varied. This is accomplished with the aid of an assumed distribution of relaxation times and frequency dependent elastic moduli