Propagating particle density fluctuations in molten NaCl
Abstract
In this paper we present the observation of acoustic modes in the spectra of molten NaCl measured over a large momentum transfer range using synchrotron radiation. A surprisingly large positive dispersion was deduced with a mode velocity exceeding the adiabatic value by nearly 70%. The large effect seems to be describable as a viscoelastic reaction of the liquid. Additionally, the derived dispersion resembles the Q-ω relation of the acoustic modes in liquid sodium. As an explanation for the large positive dispersion we propose that the density fluctuations in molten NaCl can be interpreted as a decoupled motion of the lighter and smaller cations on a nearly resting anionic background. These molten alkali halide measurements are the first experimental evidences for the so-called fast sound in a binary ionic liquid.
- Publication:
-
Physical Review B
- Pub Date:
- January 2004
- DOI:
- 10.1103/PhysRevB.69.012203
- Bibcode:
- 2004PhRvB..69a2203D
- Keywords:
-
- 61.10.Eq;
- 63.50.+x;
- X-ray scattering;
- Vibrational states in disordered systems