Density of States in Liquid and Acoustic Dissipation in Molecular Systems: From Liquid to Glass

Combined Brillouin spectra collected at visible, ultraviolet, and x-ray frequencies are used to reconstruct the acoustic loss of prototypical systems over the wide frequency range between 0.5 GHz and 5 THz. Passing from the liquid to the glassy phase [1-3], this property is found to be linearly dependent on the tagged-particle susceptibility measured by incoherent neutron scattering up to 1 THz, giving evidence of a relation between acoustic power dissipation and density of states. A simple but general formalism is presented to quantitatively explain this relation, thus clarifying the connection between the quasi-elastic component observed in neutron scattering experiments and the fast relaxation dynamics probed by Brillouin scattering [1,2]. This opens up a new way of looking at the fast dynamics of liquids and glasses. [1] L. Comez, G. Monaco, C. Masciovecchio, A. Paciaroni, A. Gessini, F. Scarponi, G. Ruocco, and D. Fioretto, Phys. Rev Lett. 106, 155701 (2011). [2L. Comez, G. Monaco, C. Masciovecchio, A. Paciaroni, A. Gessini, F. Scarponi, G. Ruocco, and D. Fioretto, J. Non Cryst-Solids. 357, 515 (2011). [3] L. Comez, S. Corezzi, A. Orecchini, A. Paciaroni, C. Petrillo, F. Sacchetti, S.C. Santucci, and D. Fioretto, J. Mol. Liq. 176, 76 (2012).