[en] We present here results of thermochromatographic model studies with Rn and Hg, conducted in order to prepare future gas-adsorption chromatographic investigations of element 112. The adsorption properties of Rn on various transition metals were investigated by vacuum thermochromatography. From the results of these experiments, predictions have been deduced for the adsorption behavior of hypothetically noble-gas-like elements 112 and 114. Empirical predictions of the adsorption interaction of a noble metallic element 112 and its lighter homologues with transition metal surfaces are given in the literature. The results of these calculations are compared with experimental data obtained in thermochromatographic model experiments with Hg. The most efficient way to chemically identify element 112 is the use of a cryo-on-line detector (COLD)-like setup, which was already successfully applied in the chemical investigation of hassium. Modifications of this device needed for the on-line thermochromatographic investigation of element 112 are presented together with results of test experiments with short-lived isotopes of Rn and Hg

[en] Results of thermochromatographic model studies with Rn and Hg, conducted in order to prepare future gas-adsorption chromatographic investigations of element 112 are represented. The adsorption properties of Rn on various transition metals were investigated by vacuum thermochromatography. From the results of these experiments predictions have been deduced for the adsorption behavior of hypothetically noble-gas-like elements 112 and 114. Empirical predictions of the adsorption interaction of a noble metallic element 112 and its homologues with transition metal surfaces are given in literature. The results of these calculations are compared with experimental data obtained in thermochromatographic model experiments with Hg. The most efficient way to chemically identify element 112 is the use of a cryo-on-line detector. Modifications of this device, needed for the on-line thermochromatographic investigation of element 112 are presented together with results of lest experiments with short-lived isotopes of Rn and Hg

[en] Carrier-free short-lived nuclides are employed in many different fields of modern nuclear chemistry. The two main production strategies are either thermal neutron-induced fission of ²³⁵U or ²³⁹Pu at nuclear reactors or spallation neutron sources or charged particle-induced nuclear reactions at accelerator facilities. An alternative method is to use a spontaneously fissioning nuclide. A facility applying this technique ('Miss Piggy') was built at the University of Berne (Switzerland). Californium-252 (²⁵²Cf), which has a 3% fission branch and a half-life of 2.645 a, is used for the production of short-lived fission products that are stopped in an adjacent recoil chamber. Short-lived nuclides are transported out of the recoil chamber using the well-known gas-jet technique. Over 100 nuclides have been identified so far and used in different applications. Since such a device does not require any large facility and is easy to operate it serves well the needs of typical university laboratories

[en] Our experiment was designed to determine thermochemical data for element 112 by measuring its adsorption enthalpy on Au to understand whether a metallic bond or a van der Waals interaction is observed. So far, the only directly produced isotope of element 112 with a sufficiently long half-life to be chemically characterized is ²⁸³112, which was produced in the nuclear fusion reaction ²³⁸U(⁴⁸Ca;3n) with a cross-section of ∝2 pb. ²⁸³112 decayed in all these studies via spontaneous fission with T_1/2 ∼ 5 min. (orig.)

[en] The prediction of the chemical properties of element 112 is difficult. From the position of element 112 in the periodic table a noble and volatile metallic character (similar to Hg) is expected. On the other hand, theoretical calculations showed, that the direct relativistic effects may affect the electron shell of element 112 very strongly, resulting in a very inert character, similar to a heavy noble gas (e.g. Rn). (orig.)

[en] An attempt to confirm production of superheavy elements in the reaction of 48Ca beams with actinide targets has been performed using the 238U(48Ca,3n)283112 reaction. Two 48Ca projectile energies were used, that spanned the energy range where the largest cross sections have been reported for this reaction. No spontaneous fission events were observed. No alpha decay chains consistent with either reported or theoretically predicted element 112 decay properties were observed. The cross section limits reached are significantly smaller than the recently reported cross sections

[en] The heaviest member of the periodic table whose chemistry has been investigated so far is element 108 (Hassium, Hs). After the discovery of long-lived superheavy elements in Dubna, Russia, the investigation of their chemical properties becomes feasible. First chemical studies are concentrating on element 112, which is expected to be a member of group 12, i.e. homologous to Hg. Numerous physico-chemical properties of element 112 and other superheavy elements have been extrapolated on the basis of the properties of the homologous elements or evaluated from relativistic calculations. In a future 112 experiment the same experimental set-up IVO (In-situ Volatilization and On-line detection) that has been successfully applied for the first ever chemical study of hassium will be used. In this device, element 112 in its elemental state will be adsorbed on PIN-detectors in a cryogenic gas thermochromatography system covering a temperature range from 0 deg C to -170 deg C. In order to increase the adsorption temperature, the PIN-diodes will be covered by nano-layers of noble metals such as Au, Pd or Pt. In order to properly select the best-suited metal, off-line thermochromatography studies with carrier-free amounts of Hg isotopes on noble metals have been performed. The experiments yielded adsorption enthalpies of Hg on these surfaces. These investigations were followed by on-line experiments at the PSI-PHILIPS cyclotron where short-lived Hg-isotopes were produced in the reaction ¹⁶⁸Yb (²⁰Ne,xn) ^180-182Hg and continuously transported in He gas to the IVO apparatus. First results of these on-line studies will be outlined. (author)

[en] One of the most exciting results of the transactinide research within the last 5 years was the observation of isotopes of transactinide elements 112-116, in ⁴⁸Ca-induced nuclear fusion reactions with actinide targets. However, the assignment of the observed nuclides to new elements is performed only via the determination of their masses and according to their measured decay properties. Thus, the unambiguous assignment of the observed nuclides to specific elements is problematic. Chemical investigations of these nuclides may help to determine indirectly their atomic number Z. Hereby, difficulties may arise from the increasing strength of the influence of the relativity principle on the electron structure with the increasing nuclear charge of the heaviest elements. The amount of these so-called relativistic effects determines the chemical behavior of the transactinide elements. Due to the uncertainty of this influence, the predictions of volatility for the superheavy elements 112-118 yield broadly ranging values. (orig.)

[en] We present results of the second experiment on the chemical identification of element 112. Similar to the first test in 2000, we aimed at the production of the spontaneously fissioning ²⁸³ with 233-MeV ⁴⁸Ca ions (the energy in the middle of the target layer). The nuclei recoiling from the target were thermalized in flowing helium. The target chamber was connected through a 25 m long capillary to detectors of α-particles and fission fragments. All the equipment and detectors were kept at ambient temperature. According to the test experiments, of all the heavy elements produced in the bombardment, only Hg, Rn and At could be transported to the detectors. The first detecting device was similar to that used earlier - an assembly of 8 pairs of PIPS detectors coated with gold. Here one would observe the decay of element 112 atoms if they like Hg adsorbed on gold. The atoms which were not retained and freely passed through the PIPS detectors entered a new, flow-through ionization chamber, 5000 cm³ in volume, optimized for detecting fission fragments. The PIPS detectors and the ionization chamber were placed inside a large assembly of ³He - filled neutron counters to detect prompt neutrons from the fission events. In 22.5 days, a beam dose of 2.8 x 10¹⁸ ions was accumulated. More than 95% of the simultaneously produced α-active ¹⁸⁵Hg (T_1/2 = 49 s) were found deposited already on the first pair of PIPS detectors; meanwhile, all the PIPSs did not detect any fission event. In the ionization chamber, eight fission events were observed in coincidence with neutron counts while the expected background was insignificant. Hence, the spontaneous fissions of the volatile activity can be conclusively attributed to the decay of element 112 produced in the fusion reaction ⁴⁸Ca + ²³⁸U, and formerly observed in Dubna physical experiments. Evaluation of the experimental data in terms of the adsorption enthalpies indicates much weaker interaction of element 112 with Au than that of Hg. One can conclude that in the given chemical environment, element 112 behaves like Rn rather than like Hg. The formation cross section of ²⁸³112 estimated from the data amounts to several pb. The experiments were carried out at the Flerov Laboratory of Nuclear Reactions at JINR in November-December 2001. (orig.)

No abstract available