On-line Gas Phase Chromatography with Chlorides of Niobium and Hahnium (Element 105)

Α. Türler, Β. Eichler, D. T. Jost, D. Piguet, H. W. Gäggeler, Κ. E. Gregorich, Β. Kadkhodayan, S. A. Kreek, D. M. Lee, M. Mohar, E. Sylwester, D. C. Hoffman (+1 others)
On-line gas chromatography / Group 5 elements / Hahnium (element 105) / Chlorides / Relativistic effects Summary The retention behavior of volatile chlorides and oxychlorides of short-lived isotopes of group 5 elements Nb and 105 (Ha = hahnium) in quartz columns was studied using on-line isothermal gas chromatography. The 15-s " 8 Nb was produced from a 215 U-fission target at a reactor neutron beam line and 34-s 262 Ha in fusion reactions of ' 8 0 + 249 Bk. The reaction products were
more » ... ucts were continuously and rapidly transported to the chromatography apparatus with a carbon aerosol gas-jet system using He as carrier gas. Volatile chloride molecules were formed in a 900°C reaction oven by adding HCl as reactive gas. Depending on trace amounts of 0 2 in the system, either the pentachlorides or the oxytrichlorides, or a mixture thereof, were formed. The isotopes "»Nb and 262 Ha were unambiguously identified after gas chromatographic separation by measuring the characteristic y-lines of " g Nb and by registering 262 Ha-25 *Lr mother-daughter a-a correlations as well as spontaneous fission decays, respectively. The adsorption enthalpies of the investigated species on quartz surfaces were determined by analyzing the measured retention curves with a Monte Carlo model. Using an empirical correlation, the adsorption enthalpies were converted to sublimation enthalpies. The sublimation enthalpies of 95 ± 16 kJ-mol" 1 and 124± 16 kJ · mol"' determined for NbCl s and NbOCl 3 , respectively, were in good agreement with literature data. In experiments with Ha-chlorides a yield curve with two components was observed. Sublimation enthalpies of ^ 120 kJ · mol -1 and 152 ±18 kJ-mol"' were estimated for HaCl 5 and HaOCl 3 , respectively. The estimated sublimation enthalpies were compared with theoretical predictions from relativistic calculations and with empirical extrapolations of chemical properties. In agreement with empirical extrapolations, a lower volatility was found for HaOCl 3 than for NbOCl·,. source: https://doi.org/10.7892/boris.115314 | downloaded: 25.9.2020
doi:10.7892/boris.115314 fatcat:soiqcwsmgbbkzlnlthimmba72y