Shear propagation in the terahertz dynamics of water-glycerol mixtures

Abstract

Inelastic X-ray and neutron scattering techniques were jointly used to investigate the dynamics of water-glycerol mixtures at different concentrations and temperatures. It was observed that even relatively low concentrations of glycerol increase the damping of shear modes, as a consequence of the known ability of glycerol to disrupt the hydrogen bond network of water. A similar trend was observed when increasing the temperature, which suggests the presence of a locus in the concentration-temperature plane marking a crossover in the shear modulus.

Structural Evolution of Supercritical CO2across the Frenkel Line

“…Supercritical fluids have started to be employed in several important applications, ranging from the extraction of floral fragrance from flowers to applications in food science such as creating decaffeinated coffee, pharmaceuticals, polymers, cosmetics, functional food ingredients, powders, bio-and functional materials, natural products, nano-systems, biotechnology, fossil and biofuels, microelectronics, energy and environment. The development of new experimental methods and improvement of existing ones continues to play an important role in this field [15][16][17][18][19][20], with the ongoing effort in elucidating and understanding the structure and properties of disordered matter such as glasses and liquids [21][22][23][24][25][26].…”

Using X-ray as a Probe of the Terahertz Dynamics of Disordered Systems – Complementarity with Inelastic Neutron Scattering and Future Perspectivess

“…However, nowadays, this interpretation needs some reconsideration because the L-T coupling was also observed in non-tetrahedral systems, such as glassy glycerol [54] and liquid metals [55][56][57][58][59]. Furthermore, a similar effect was reported in more complex systems such as binary mixtures [51] and biophysical samples [60][61][62].…”

“…A possible method to circumvent these complementary limitations foresees simultaneous IXS and INS measurements on the same heavy water sample. This is the strategy followed by joint INS-IXS measurement in heavy water [50] and in a successive one on deuterated water-glycerol mixtures [51]. The use of deuterated samples was, of course, imposed by the highly incoherent INS cross section of hydrogen, which would have prevented the INS measurement to reliably determine the coherent spectrum.…”

“…All reported curves are normalized to the S(Q) for consistency. Data are redrawn with permission from Ref [51],. which is copyrighted by the American Physical Society.…”

The Spectrum of Density Fluctuations of Noble Gases Probed by THz Neutron and X-ray Spectroscopy

“…Fortunately, for simplest systems as noble gases, of interest in this paper, it is reasonable to assume that the simple exponential decay is a rather accurate approximation. (2) A second remark concerns the possible presence in the spectrum of a second inelastic excitation as observed in systems as diverse as liquid water [73,[76][77][78], tetrahedrally arranged glasses [79], glass formers [80] liquid metals [81][82][83][84][85], complex biophysical samples [86][87][88] and mixtures [89]. The presence of this low frequency mode in the S(Q,ω) is customarily ascribed to the onset of shear mode propagation, although this assignment could seem suspicious as S(Q,ω) couples primarily with longitudinal movements only.…”