CHEMICAL IDENTIFICATION OF ELEMENT 106
( Thermochromatography of Oxochlorides)

I.Zvara, A.B.Yakushev, S.N.Timokhin, Xu Honggui, V.P.Perelygin, and Yu.T.Chuburkov:(JINRPreprint E12-97-102, Dubna, 1997.; submitted to Radiochimica Acta).

Experiments performed during past four years have resulted in first chemical identification of element 106. Bombardments of ²⁴⁹Cf with ¹⁸O ions in a total lasted 90 hours, and as many as 40 atoms of the element (presumably mass number 263, T_1/2 = 1 s) isolated from the mixture of the products were recorded. Specifically, to prove the chemical individuality of element 106, it was separated from elements 105, 104 and heavy actinoids.

The element was detected by its spontaneous fission, and the chemical separation technique was essentially the thermochromatography of oxochlorides (see Figure). The thermalized recoils swept from a target chamber by flowing gas are treated by a gaseous chlorinating agents and oxygen to produce volatile oxochlorides. They are characteristic of group VI transition metals – W, Mo, and Cr, while element 106 is expected to have a character of eka-tungsten. In a silica column with an imposed negative temperature gradient, volatile compounds of various elements are deposited in different temperature ranges according to their adsorption energies. The latter are known to correlate with “macroscopic volatility” of the species. The inner wall of the column served as the solid state track detector of fission fragments from the decay of element 106. The tracks could be revealed after the end of a long lasting continuous experiment by etching the surface and scanning it for the tracks with an optical microscope.

The white histogram demonstrates fission events observed with a cold inert gas – all the atoms are irreversibly deposited near the inlet of the column. The stacked hatched histogram shows the fission events recorded in three independent chemical experiments. Now, element 106 produces a zone with a characteristic profile, as one can see from the peak shape of a simultaneously produced longer-lived tungsten isotope (in the chemical state of an oxochloride), which could be traced by its gamma-radiation.

This first identification was performed with a relatively good statistics. So it also provides first quantitative data on the difference in properties between eka-W (106) and W. Such results are of utmost importance in view of the challenging problem of the so called relativistic effects in the chemical properties of the heaviest elements.

CHEMICAL IDENTIFICATION OF ELEMENT 108

Hassium confirms its position in the Periodic Table.
For the first time Element 108 has been chemically identified by six atoms.

Thanks to the new experimental techniques developed in the international collaboration - Paul Scherrer Institute (PSI), the University of Bern in Switzerland, GSI, Institute of Nuclear Chemistry in Mainz, Germany, LBNL (USA) and FLNR (Dubna, Russia) - the element named after the Land Hesse (Germany) has found its place in the Periodic Table.

Element 108 was synthesized at GSI (Darmstadt, Hesse, Germany) in 1984 but only now and thanks to cooperative efforts of scientists from Switzerland, Germany, Russia, USA and China its first chemical study has been performed. Hassium (Hs)'s six decay chains have been registered and two of them belong to the newly discovered in this experiment ²⁷⁰Hs. It was discovered that hassium like its nearest homologues Ru and Os forms an extremely volatile compound with oxygen. This proves that it belongs to the eighth group of the Periodic Table. Its atomic number is 108 so hassium is for a while the heaviest element studied chemically.

Hs atoms have been got in a fusion reaction ²⁴⁸Cm with ²⁶Mg bombarding particles at UNILAC accelerator in Darmstadt and they exist only for a few seconds. Formation's small cross-section involved high- intensity ²⁶Mg beam. To settle this problem the new radiation technology has been realized in GSI - rotating vacuum window and target separated accelerator's vacuum and target chamber gas space.

New gas-chemical separation method developed collectively by chemists from FLNR, PSI and the University of Bern allowed to convert synthesized atoms to volatile compound over oxygen and highly effectively transform it to the detector setup in the gas flow. The detector setup is a narrow gas channel of silicon detectors with negative temperature gradient from 0^oC up to 170^oC, it was created at PSI in cooperation with LBNL.

Successful experiment opens new and inviting prospects for future chemical experiments with heavier elements.

Editorial note. We got this information from a participant in the experiment Alexander Yakushev who works in Darmstadt at the moment. Press release has been prepared practically by all collaborators together. As for the FLNR contribution, - added Alexander in his later message,- chemical extraction method belongs to us, separation principle is ours as well, detection principle belongs to LBNL. PSI totalized everything, GSI prepared new construction of the target that allowed the chemists to accept very high intensity.

Chemical investigation of hassium (element 108)
Nature 418, 859 - 862 (2002); doi:10.1038/nature00980
CH. E. DULLMANN*†, W. BRUCHLE‡, R. DRESSLER†, K. EBERHARDT§, B. EICHLER†, R. EICHLER†, H. W. GAGGELER*†, T. N. GINTER , F. GLAUS†, K. E. GREGORICH , D. C. HOFFMAN , E. JAGER‡, D. T. JOST†, U. W. KIRBACH , D. M. LEE , H. NITSCHE , J. B. PATIN , V. PERSHINA‡, D. PIGUET†, Z. QIN#, M. SCHADEL‡, B. SCHAUSTEN‡, E. SCHIMPF‡, H.-J. SCHOTT‡, S. SOVERNA*†, R. SUDOWE , P. THORLE§, S. N. TIMOKHIN , N. TRAUTMANN§, A. TURLER**, A. VAHLE††, G. WIRTH‡, A. B. YAKUSHEV & P. M. ZIELINSKI
* Departement fur Chemie und Biochemie, Universitat Bern, CH-3012 Bern, Switzerland
† Labor fur Radio- und Umweltchemie, Paul Scherrer Institut, CH-5232 Villigen, Switzerland
‡ Gesellschaft fur Schwerionenforschung mbH, D-64291 Darmstadt, Germany
§ Institut fur Kernchemie, Universitat Mainz, D-55128 Mainz, Germany
Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
Department of Chemistry, University of California, Berkeley, California 94720-1460, USA
# Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, P.R. China
Flerov Laboratory of Nuclear Reactions, Joint Institute for Nuclear Research, 141980 Dubna, Russia
** Institut fur Radiochemie, Technische Universitat Munchen, D-85748 Garching, Germany
†† Research Center Rossendorf e.V., D-01314 Dresden, Germany
Correspondence and requests for materials should be addressed to H.W.G. (e-mail: gaeggeler@iac.unibe.ch).

The periodic table provides a classification of the chemical properties of the elements. But for the heaviest elements, the transactinides, this role of the periodic table reaches its limits because increasingly strong relativistic effects on the valence electron shells can induce deviations from known trends in chemical properties. In the case of the first two transactinides, elements 104 and 105, relativistic effects do indeed influence their chemical properties, whereas elements 106 and 107 both behave as expected from their position within the periodic table. Here we report the chemical separation and characterization of only seven detected atoms of element 108 (hassium, Hs), which were generated as isotopes ²⁶⁹Hs (refs 8, 9) and ²⁷⁰Hs (ref. 10) in the fusion reaction between ²⁶Mg and ²⁴⁸Cm. The hassium atoms are immediately oxidized to a highly volatile oxide, presumably HsO₄, for which we determine an enthalpy of adsorption on our detector surface that is comparable to the adsorption enthalpy determined under identical conditions for the osmium oxide OsO₄. These results provide evidence that the chemical properties of hassium and its lighter homologue osmium are similar, thus confirming that hassium exhibits properties as expected from its position in group 8 of the periodic table

A. Yakushev's Interview to "Nature" on Element 112
From Kendall Powell's article "Heavy elements: A very brief encounter"
Nature 418, 815 - 816 (2002); doi:10.1038/418815a

Deviant behaviour
One element, however, looks set to throw the rulebook away completely. A team led by Alexander Yakushev at the Flerov Laboratory of Nuclear Reactions in Dubna, Russia, is currently trying to capture element 112. This element is in group 12, so it ought to behave like a more volatile version of mercury. But relativistic effects are expected to make some of its properties more like those of an inert gas such as radon7.
Yakushev and his colleagues decided to hedge their bets by building an experimental set-up to detect both mercury-like and radon-like activity. Unlike the hassium experiment, the group is assessing the chemistry of element 112 in its unbonded state. Calcium ions are smashed into a uranium target, and the atoms of element 112 that are created are flushed onto two different detectors. If the element behaves like mercury, it should bind to the gold-covered surface of one of the detectors. If it doesn't, it will be swept into an ionization chamber where its radioactive decay chain will be detected. In preliminary, unpublished results, nothing stuck to the gold surface, but eight atoms were detected in the chamber, indicating that 112 may display radon-like properties. Other elements disrupt the trends within their groups, but 112 appears to be acting as if it belongs to another group altogether.
Like other work on the chemistry of heavy elements, the Flerov team relies heavily on techniques and predictions developed by researchers around the world. The hassium study was an equally multinational affair. Teams at Lawrence Berkeley National Laboratory in Berkeley, California, and the Paul Scherrer Institute in Villigen, Switzerland - where Dullmann is based - designed the detectors, Flerov researchers performed preliminary studies of osmium and various German groups made the target, organized the final experiment and provided theoretical calculations. "In principle, it was everyone working in gas-phase chemistry of superheavy elements in the world," says Yakushev, who is a co-author on the hassium paper. Such collaborative spirit does not always come easily. The competition between groups to find new elements is intense, partly because the discoverers get to name the element. But the complexity of the chemistry experiments forces the groups to work together. "It requires walking a fine line and tremendous diplomacy," says Heino Nitsche, a nuclear chemist at Lawrence Berkeley.