Isotope Thermotransport in Liquid Potassium, Rubidium, and Gallium

Abstract

Temperature differences ranging from 100°C to 500°C were maintained between the top and bottom ends of vertical capillaries containing liquid metal. The light isotope was found to be enriched at the hot end. The steady-sate isotope separation for different temperature ranges were between 1 and 3 per cent, corresponding to the thermal diffusion factors αK=3.1×10-2, αRb=3.1 × 10-2 and αGa=3.8 × 10 -2. According to a theoretical model, the results imply that the diffusing species is a “cluster” of several cooperating atoms, the mean diffusive displacement of which is considerably less than the effective cluster diameter. The clusters drift into voids given by the statistical fluctuations of free volume.