On-line Gas Chromatographie Studies of Chlorides of Rutherfordium and Homologs Zr and Hf

Abstract

Gas-phase isothermal chromatography is a method by which volatile compounds of different chemical elements can be separated. The technique, coupled with theoretical modeling of the processes occurring in the chromatography column, provides information about thermodynamic properties (e.g., adsorption enthalpies) for compounds of elements, such as the transactinides, which can only be produced on an atom-at-a-time basis. In addition, the chemical selectivity of the isothermal chromatography technique provides the decontamination from interfering activities necessary for determination of the nuclear decay properties of the isotopes of these elements.<br /> The Zr and Hf isotopes, 30.7-s ⁹⁸Zr and 38-s ¹⁶²Hf were produced via the ²³⁵U(n,f) and ¹⁴⁷Sm(20Ne,5n) reactions, respectively. The 65-s ²⁶¹Rf was produced via the ²⁴⁸Cm(¹⁸O,5n) reaction. A new and more accurate half-life for ²⁶¹Rf of 78⁺¹¹_-6-s has been measured. Measurements were performed on chloride species of Rf and its group 4 homologs, Zr and Hf and on Zrbromides using the Heavy Element Volatility Instrument (HEVI). Adsorption enthalpies were calculated for all species using a Monte Carlo code simulation based on a microscopic model for gas thermochromatography in open columns with laminar flow of the carrier gas and the following adsorption enthalpies for the group 4 chlorides were obtained for quartz surfaces: Zr(-74±5 kJ/mol), Hf ( - 9 6 ± 5 kJ/mol) and Rf (—77±6 kJ/mol). These results indicate that Rf deviates from the trend expected based on extrapolation of the Zr and Hf values. Further calculations are needed to assess whether this is due to relativistic effects in the transactinide region.