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By D. T. Jost, D. Piguet (psi, T. N. Ginter, K. E. Gregorich, U. Kirbach, D. M. Lee, R. Sudowe, M. Schädel, B. Schausten, E. Schimpf, H. -j. Schött, G. Wirth (gsi, S. N. Timokhin, K. Eberhardt, P. Thörle, N. Trautmann (univ Mainz, Z. Qin (imp Lanzhou and A. Vahle


The heaviest element, whose chemical behavior has been studied so far is bohrium (Bh) with Z=107 [1] behaving like a typical member of group 7 of the periodic table. The longestlived α-decaying isotope of the next heavier element hassium (Hs, Z=108) is 269 Hs (T=11.3 s) which has been identified in the decay chain of 277 112 [2,3]. Hs is supposed to be a member of group 8 of the periodic table and should thus form a very volatile tetroxide. Relativistic density functional calculations predicted the electronic structure of HsO4 to be similar to the one of OsO4 [4]. Application of different semiempirical models of the interaction of a MeO4 molecule with quartz surface predicted the adsorption behavior of OsO4 and HsO4 to be very similar [4]. Extrapolations of trends within group 8 of the periodic table also predicted HsO4 and OsO4 to behave similar in a gas adsorption chromatography experiment [5]. Hs isotopes were produced directly in the reaction 248 26 269,270 Cm ( Mg;5,4n) Hs at the UNILAC at GSI Darmstadt [6]. Hs isotopes recoiling from the target were thermalized and oxidized in a He/O2 mixture in the recoil chamber of the In-situ Volatilization and On-line detection apparatus IVO [7]. Volatile HsO4 was transported with the carrier gas to the Cryo-On-Line-Detector (COLD), a thermochromatography device. Along a narrow channel formed of PIN-diodes registering α-decaying and spontaneously fissioning (SF) nuclides, a temperature gradient form-20 to-170 °C was established. The deposition temperature of volatile species could therefore be determined, allowing for the determination of their adsorption enthalpy. COLD is an improved version of the Cryo-Thermochromatography Separator CTS developed at Berkele

Year: 2011
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