title: Intramolecular origin of the fast relaxations observed in the brillouin light scattering spectra of molecular glass formers
abstract: The Brillouin light scattering spectra of the o-terphenyl single crystal are compared with those of the liquid and the glass phases. This shows (i) the direct evidence of a fast relaxation at frequencies nu approximately 5 GHz in both the single crystal and the glass; (ii) a similar temperature dependence for the attenuation of the longitudinal sound waves in the single crystal and the glass; and (iii) the absence of coupling between the fast relaxation and the transverse acoustic waves. These results allow us to assign such a relaxation to the coupling between the longitudinal acoustic waves and intramolecular vibrations, and therefore to exclude any relationship between it and the glass transition.
authors.affiliation: European Synchrotron Radiation Facility, Boite Postale 220, F-38043 Grenoble Cedex, France.
authors.initials: G
authors.lastname: Monaco
authors.initials: S
authors.lastname: Caponi
authors.lastname: Di Leonardo R
authors.initials: D
authors.lastname: Fioretto
authors.initials: G
authors.lastname: Ruocco