High-frequency transverse-like excitations in glassy glycerol

• Published in: Philosophical magazine (2003. Print) 2004-05, Vol.84 (13-16), p.1453-1461
• Main Authors: Scopigno, Tullio, Pontecorvo, Emanuele, Leonardo, Roberto Di, Krisch, Michael, Monaco, Giulio, Ruocco, Giancarlo, Ruzicka, Barbara, Sette, Francesco
• Format: Article
• Language: English
• Subjects: Brillouin and rayleigh scattering; other light scattering; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Disordered solids; Exact sciences and technology; Glasses; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Physics; Structure of solids and liquids; crystallography
• ISSN: 1478-6435; 1478-6443
• DOI: 10.1080/14786430310001644215

The dynamic structure factor of glassy and liquid glycerol has been measured by inelastic X-ray scattering in the exchanged momentum Q region Q=2-23 nm −1 and in the temperature range 80-570 K. Besides the propagating longitudinal mode, at low temperatures the spectra show a second non-Q-dispersing peak at ≈ 8.5 meV. This peak is the signature of the transverse dynamics which, in topologically disordered systems, acquire a small Q-dependent longitudinal symmetry component. This assignment is substantiated by a study of the temperature dependence of the intensity of the second peak. This study showed that, in the liquid, the second peak intensity vanishes when the structural relaxation time τ α approaches , a behaviour consistent with the condition τ α Ω T ≫1 required for the existence of a non-relaxational transverse-like dynamics in the liquid state.