Ellipsometric Study of the Complex Dielectric Function of K_xKCl_1‐x Approaching the NM‐M Transition

Abstract

Metals / Molten Salts / Optical PropertiesWe report the first ellipsometric measurements of the optical constants, refractive index n and absorption coefficient k, for a fluid system at high temperatures, i.e. salt rich K,KCI,li solutions up to 800°C. The applicability and realization of the ellipsometric technique under these experimental conditions is described in detail. First data of the optical conductivity u(w,x) and the real part of the dielectric function E , ( W , X ) are presented. In a qualitative discussion of these results emphasis is given on the NM-M transition region. The behaviour of ~( o ,x) in the IR-region indicates the occurrence of metal clustering approaching the NM-M transition. From the dielectric anomaly of E , (x) it is concluded that the onset of metallic behaviour is well separated from the consolute composition of the critical point of liquidliquid immiscibility.