Europhys. Lett.
Volume 75, Number 1, July 2006
Page(s) 70 - 76
Section Condensed matter: structural, mechanical and thermal properties
Published online 02 June 2006
Europhys. Lett., 75 (1), pp. 70-76 (2006)
DOI: 10.1209/epl/i2006-10091-y

Adiabatic and isothermal sound waves: The case of supercritical nitrogen

F. Bencivenga1, A. Cunsolo2, M. Krisch1, G. Monaco1, G. Ruocco3 and F. Sette1

1  European Synchrotron Radiation Facility - B.P. 220, F-38043 Grenoble Cedex, France
2  CRS SOFT-INFM-CNR - Operative Group in Grenoble c/o ILL B.P. 220, F-38043 Grenoble Cedex, France
3  Dipartimento di Fisica and CRS SOFT-INFM-CNR Università di Roma "La Sapienza" - Roma, Italy

received 18 January 2006; accepted in final form 12 May 2006
published online 2 June 2006

The acoustic sound dispersion of nitrogen in its liquid and supercritical phase has been studied by Inelastic X-Ray Scattering (IXS). Approaching supercritical conditions, the gradual disappearance of the positive sound dispersion, characteristic of the low-temperature liquid, is observed. In the supercritical state, evidence for a crossover between adiabatic and isothermal sound propagation regimes is inferred by an analysis of the dynamic structure factor based on generalized hydrodynamics.

61.10.Eq - X-ray scattering (including small-angle scattering).
63.50.+x - Vibrational states in disordered systems.
61.20.-p - Structure of liquids.

© EDP Sciences 2006