Thermochromatography of Heavy Actinides - Determination of the Sublimation Enthalpy of Es

The adsorption of Cf, Es, and Fm on several metals was studied thermochromatographically. In all systems investigated Es is adsorbed between the Cf and Fm, due to the increasing metallic divalency in the second half of the actinide series. Based on the adsorption data and the experimentally proved correlation between adsorption and sublimation heats we calculated the Es sublimation enthalpy of 167 kj/mol. This is significantly higher than the value obtained by direct vapour pressure measurements (133 kJ/mol [1]). However, this value fits better to theory