Gas Phase Chromatography Experiments with Bromides of Tantalum and Element 105

Abstract

The retention behavior of volatile bromide molecules of short-lived isotopes of tantalum and element 105 in KCl coated quartz columns was studied using continuous isothermal gas chromatography. HBr and HBr saturated with BBr₃ vapor were used as reactive gases. The isotopes were produced in the fusion reactions ²⁰Ne+^nat.Eu and ¹⁸O + ²⁴⁹Bk, respectively. The reaction products were transported from the accelerator to the chromatography set-up with a gas-jet system using an aerosol with He as carrier gas and KCl as transporting particles. The measured retention times are compared to those of ⁹⁹^gNb bromides from a previous study. The retention times of niobium and tantalum bromides are very similar, in agreement with expectations based on the nearly identical sublimation enthalpies of NbBr₅ and TaBr₅. For the bromides of element 105, higher retention times are found, indicating a lower volatility of 105Br₅ than of NbBr₅ and TaBr₅. On the basis of empirical systematics, a sublimation enthalpy of 138 ± 15 kJ/mol can be estimated for 105Br₅ from the experimental data.