Direct detection of fluctuations in liquids - new approach for liquid-liquid phase transition
by
Y. Kajihara(Hiroshima University, Japan)
→
Europe/Rome
Aula 8 (Dipartimento di Fisica - Ed. E. Fermi)
Aula 8
Dipartimento di Fisica - Ed. E. Fermi
Description
As is well known, liquid water at ambient condition exhibits many thermodynamic anomalies. In recent study, these anomalies are thought to be derived from the transition between low-density and high-density water, but the hypothesis has not been proved yet by the experiment, mainly because the real transition is hidden in the deep supercooled "no-man's land". We take original approach to this problem. We focus on mesoscopic fluctuations that should exist in a wide temperature and pressure area around the transition region, which means we do not have to reach "no-man's land" to discuss the existence of it. To detect fluctuations directly, we propose a new experimental method utilizing "fast sound" phenomena, which is also known as an anomalous feature of liquid water. The fast sound is a historical expression that the sound velocities of liquid water obtained by the microscopic methods (molecular dynamics, inelastic neutron / x-ray / ultraviolet scattering) are much higher than that by the macroscopic one (ultrasonic sound) and now similar phenomena are observed in some other liquid systems. We have carried out inelastic x-ray scattering (IXS) measurement for liquid water at high temperatures and high pressures at SPring-8 in Japan. We also carried out IXS and small-angle x-ray scattering (SAXS) measurements for liquid chalcogen (Se-Te) system which is known to show anomalous thermodynamics such like water and exhibit continuous liquid- liquid phase transition. In the talk, I will show the experimental results and discuss the theoretical basis of the method, and finally comment on the perspective of liquid study by using it.
