Possibility of generation of octavalent curium in the gas phase in the form of volatile tetraoxide CmO4

Abstract

Experiments based on gas thermochromatography were performed with the aim to search for volatile tetraoxide CmO4 in the products of thermal oxidation of microamounts of CmH2–3. The carrier gas was He, and the reagent gas was O2. At their equimolar ratio, the zone of deposition of volatile Cm species at negative temperatures, centered at −80°C, was detected on the quartz column surface. The thermochromatographic peaks formed by plutonium tetraoxide and by the volatile Cm species are similar in shape. The enthalpy of adsorption of this species on the quartz surface was calculated to be −47 ± 12 kJ mol−1. The data obtained are compared to the results of previous experiments with PuH2–3. The chemical behavior of the volatile Cm species at decreased O2 concentration in the carrier gas (1 and 5%) was studied. It resembles the previously studied behavior of PuO4 under similar conditions. It was concluded that the volatile Cm species has the formula CmO4.