Brillouin scattering study of salol: Exploring the effects of rotation-translation coupling

Abstract

Brillouin scattering in liquids composed of optically and mechanically anisotropic molecules is affected by coupling between rotational and translational dynamics. While this effect has been extensively studied in depolarized (VH) scattering where it produces the "Rytov dip," recent theoretical analyses by Pick, Franosch show that it should also produce observable effects in polarized (VV) scattering [Eur. Phys. J. B 31, 217 (2003)]; 31, 229 (2003)]]. To test this theory, we carried out Brillouin scattering studies of the molecular glassformer salol in the temperature range 210-380 K, including VH-backscattering, VH-90 degrees, and VV-90 degrees spectra. The data were analyzed consistently to determine the effects of rotation-translation coupling on both the polarized and depolarized spectra. A previously unanticipated feature predicted by these authors was observed: a narrow negative region in the q -dependent part of the 90 degrees VV spectra, which we designate as the "VV dip." It is an analog of the Rytov dip observed at high temperatures in the 90 degrees VH spectra, which is also accurately described by this theory. Analysis of the 90 degrees VV spectra was carried out both with and without inclusion of translation-rotation coupling in order to determine quantitatively the role this coupling plays.

Heat capacity, Raman, and Brillouin scattering studies of M2O–MgO–WO3–P2O5 glasses (M=K,Rb)

“…One of a very powerful tool in studies of glasses is Brillouin spectroscopy since it has been shown to give valuable information on the dynamical properties of glass-forming materials in the gigahertz region. [1][2][3][4][5][6][7][8] The relaxational processes have been extensively studied for glass formers without directional bonds, which show a similar high increase of viscosity upon supercooling and are called fragile systems. 3,6,7 The dynamics of these fragile systems is relatively well understood on the basis of mode coupling theory.…”

“…[1][2][3][4][5][6][7][8] The relaxational processes have been extensively studied for glass formers without directional bonds, which show a similar high increase of viscosity upon supercooling and are called fragile systems. 3,6,7 The dynamics of these fragile systems is relatively well understood on the basis of mode coupling theory. 6,9 On the other hand, in the presence of directional bonds the temperature variation of viscosity is weaker, and the dynamics of these so-called strong and intermediate glass formers is still not well understood.…”

“…3,6,7 The dynamics of these fragile systems is relatively well understood on the basis of mode coupling theory. 6,9 On the other hand, in the presence of directional bonds the temperature variation of viscosity is weaker, and the dynamics of these so-called strong and intermediate glass formers is still not well understood. 8,10 It is, therefore, of great interest to study strong and intermediate glass formers in a broad temperature range in order to understand how the presence of directional bonds influences the various properties of glasses.…”

The Prigogine–Defay ratio and the microscopic theory of supercooled liquids

“…14 The same is true in the case of metatoluidine 15 for s ͑t͒, ͑t͒, and L ͑t͒. For instance, in the molecular liquid salol, it has been recently shown that the relaxation times and stretching coefficients of s ͑t͒ and ⌫͑t͒ are different.…”

Brillouin Scattering and its Application in Geosciences

“…With decreasing temperature, these additional features progressively narrow down and eventually collapse in an unresolved single line as a consequence of the viscoelastic behavior of the material, up to the appearance of two transverse acoustic modes (Brillouin peaks) at even lower temperature in the solid state (Patterson 1976). New macroscopic and microscopic theoretical analyses of scattering from coupling of molecular rotation-translation dynamics of anisotropic molecular fluids have been recently tested by new experimental observations (Zhang et al 2004). Recently, Brillouin scattering has been used to monitor the time-progress of the photo-induced polymerization of binary mixtures of monomer organic compounds as a function of their composition and of temperature (Ziobrowski et al 2011).…”