Critical opalescence and the true dielectric state in a Coulomb system

Abstract

To study the critical opalescence effect in a two-component Coulomb system consisting of single-type electrons and nuclei, we consider the limit relations for static structure factors and analyze the singularities of the dielectric permittivity. We show that the critical opalescence effect can be observed not only at the critical point corresponding to the gas-liquid phase transition but also near the true dielectric state with zero static conductivity. With the available experimental data taken into account, we assume that the true dielectric state is the limit state of the liquid-liquid phase transition accompanied by sharp variations in the electrical conduction of the substances. We find that if the thermodynamic parameters correspond to the true dielectric state, then the critical opalescence effect can arise in the case where the squared fluctuation in the total number of electrons and nuclei in a two-component Coulomb system becomes infinite, as this occurs at the critical point corresponding to the gas-liquid phase transition.

An undergraduate laboratory experiment to determine the critical point of SF6 using light scattering at selected wavelengths

“…A review of these methods for particle characterization can be found in [7], whereas [8] presents theoretical light scattering techniques including that of opalescence in condensed matter. The thermodynamics of critical points and the associated opalescence are finding new application in ultra-cold physics [9] and in Bose-Einstein condensates [10], and recent work has been carried out considering opalescence in dielectric media [11]. These new studies demonstrate this area continues to have topicality in emerging areas of physics.…”