Optical Study of Electron Localization Approaching a Polarization Catastrophe in LiquidKx−KCl1−x

Abstract

The absorption constant $K\left(\nu \right)$ and refractive index $n\left(\nu \right)$ have been measured at photon energies of $0.5<~h\nu <~5.5$ eV in liquid ${\mathrm{K}}_x-\mathrm{K}{\mathrm{Cl}}_{1-x}$ solutions for $0.001<~x<~0.05$ and temperatures up to 900°C, approaching the metal-nonmetal transition. The absorption spectra give clear evidence for $F$-center states existing at all $x$ in equilibrium with aggregated centers, probably small metal clusters. The dielectric susceptibility increases with $x$ by almost 2 orders of magnitude. A fit of the dielectric enhancement by a critical form yields a critical exponent, $\zeta =1.4\mathrm{}\pm 0.2$.