The dispersive behavior of collective excitations in fluids: an experimental test for the generalized collective modes theory.

The predictions of the generalized collective modes (GCM) theory on the non-hydrodynamic dispersion of collective excitations of liquids and supercritical fluids have been tested against previous inelastic x-ray scattering measurements on samples of increasing complexity. We observed a good agreement between experimental results and theoretical predictions within the hypothesis that sound propagation is adiabatic. Overall, the performed comparison provides an experimental validation of GCM predictions and shows that, even in the transition region between the hydrodynamic and the mesoscopic regimes, thermal fluctuations have a minor influence on the dispersion, whose non-hydrodynamic effects are mostly driven by viscoelastic phenomena.

[1]  T. Bryk.  Non-hydrodynamic collective modes in liquid metals and alloys , 2011 .

[2]  G. Ruocco,et al.  Collective excitations in supercritical fluids: analytical and molecular dynamics study of "positive" and "negative" dispersion. , 2010, The Journal of chemical physics.

[3]  G. Ruocco,et al.  The Widom line as the crossover between liquid-like and gas-like behaviour in supercritical fluids , 2010 .

[4]  G. Ruocco,et al.  High frequency dynamics in liquids and supercritical fluids: A comparative inelastic x-ray scattering study. , 2009, The Journal of chemical physics.

[5]  I. Mryglod,et al.  Ab initio study of dispersion of optic-like modes in a molten salt: Effect of ion polarization , 2008 .

[6]  G. Ruocco,et al.  High-frequency dynamics of liquid and supercritical water. , 2007, Physical review. E, Statistical, nonlinear, and soft matter physics.

[7]  A. Cunsolo,et al.  Structural relaxation in the dynamics of glycerol: a joint visible, UV and x-ray inelastic scattering study , 2006 .

[8]  G. Ruocco,et al.  Adiabatic and isothermal sound waves: The case of supercritical nitrogen , 2005, cond-mat/0512383.

[9]  G. Ruocco,et al.  Microscopic dynamics in liquid metals: The experimental point of view , 2005, cond-mat/0503677.

[10]  F. Scarponi,et al.  Brillouin light scattering from transverse and longitudinal acoustic waves in glycerol , 2004 .

[11]  G. Ruocco,et al.  Brillouin scattering investigations of fast dynamics in glass forming systems , 2002 .

[12]  G. Ruocco,et al.  Structural and microscopic relaxation processes in liquid hydrogen fluoride. , 2002, Physical review letters.

[13]  I. Mryglod,et al.  Collective dynamics in liquid lead: generalized propagating excitations. , 2001, Physical review. E, Statistical, nonlinear, and soft matter physics.

[14]  G. Ruocco,et al.  Microscopic relaxation in supercritical and liquid neon , 2001 .

[15]  G. Ruocco,et al.  Relaxation processes in harmonic glasses? , 2000, Physical review letters.

[16]  G. Ruocco,et al.  Viscoelastic behavior of water in the terahertz-frequency range: an inelastic x-ray scattering study. , 1999, Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics.

[17]  G. Ruocco,et al.  Dynamics of Glasses and Glass-Forming Liquids Studied by Inelastic X-ray Scattering , 1998 .

[18]  G. Ruocco,et al.  HIGH FREQUENCY SOUND WAVES IN VITREOUS SILICA , 1998, cond-mat/9801210.

[19]  G. Ruocco,et al.  MIXING OF LONGITUDINAL AND TRANSVERSE DYNAMICS IN LIQUID WATER , 1997 .

[20]  A. Cunsolo,et al.  VELOCITY DISPERSION AND VISCOUS RELAXATION IN SUPERCOOLED WATER , 1996 .

[21]  Bergmann,et al.  Transition from Normal to Fast Sound in Liquid Water. , 1996, Physical review letters.

[22]  I. Omelyan,et al.  Generalized collective modes for the Lennard-Jones fluid , 1995 .

[23]  I. M. Schepper,et al.  Mode-coupling effects in the density dependence of the shear viscosities of dense argon and methane , 1989 .

[24]  F. Wanderlingh,et al.  Evidence of anomalous acoustic behavior from Brillouin scattering in supercooled water , 1984 .

[25]  M. Ernst,et al.  Theory of Transport Coefficients for Moderately Dense Gases , 1969 .

[26]  H. Mori.  Transport, Collective Motion, and Brownian Motion , 1965 .

[27]  J. CLERK-MAXWELL,et al.  O ver de contimiiteit van den gas- en vloeistofiocstand Academisch proefschrift , 1874, Nature.