Adiabatic and isothermal sound waves: The case of supercritical nitrogenF. 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