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

Türler, Α.; Eichler, Β.; Jost, D. T.; Piguet, D.; Gäggeler, H. W.; Gregorich, Κ. E.; Kadkhodayan, Β.; Kreek, S. A.; Lee, D. M.; Mohar, M.; Sylwester, E.; Hoffman, D. C.; Hübener, S. (1996). On-line Gas Phase Chromatography with Chlorides of Niobium and Hahnium (Element 105). Radiochimica acta, 73(2), pp. 55-66. Oldenbourg 10.1524/ract.1996.73.2.55

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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 iso-thermal gas chromatography. The 15-s "8Nb was produced from a 215U-fission target at a reactor neutron beam line and 34-s 262Ha in fusion reactions of '80 + 249Bk. The reaction products 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 02 in the system, either the pentachlorides or the oxytrichlorides, or a mixture thereof, were formed. The isotopes "»Nb and 262Ha were unambiguously identified after gas chromatographic separation by measuring the characteristic y-lines of "gNb and by registering 262Ha-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 NbCls and NbOCl3, 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 HaCl5 and HaOCl3, 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 HaOCl3 than for NbOCl3.

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