At GSI Darmstadt a ²³⁸U target was bombarded by ⁴⁸Ca ions in order to form the isotope ²⁸³112. This nuclide is produced in a complete fusion reaction followed by the evaporation of 3 neutrons. ²⁸³112 has a half-life of several minutes and decays via spontaneous-fission (SF).
During a 17 day beam time the reaction products were collected in a He recoil chamber and continuously transported to a counting device. In addition, short-lived radioactive isotopes of Hg and Rn were added to the gas transport system. The carrier gas was injected into an array of 32 Au-covered Si detectors that were kept at different temperatures between +35 (first detector) and -185 °C (last detector). The figure depicts the results of the experiment: as expected, in the first detectors Hg is adsorbed, whereas Rn adsorbed at the very end of the array (upper part). In addition, at -170 °C 7 SF events were observed which can be assigned to the decay of ²⁸³112 (lower part). The 4 additional SF events distributed randomly along the array are considered to be back-ground. This first result on the thermochemical behaviour of element 112 indicates a Rn-like behaviour, presumably caused by relativistic effects on the atomic orbitals of this closed 7s²6d¹⁰ shell element (group 12).

This work was carried out in the group of Prof. Heinz W. Gäggeler.

References:

• A. B. Yakushev, I. Zvara, Yu. Ts. Oganessian, A. V. Belozerov, S. N. Dmitriev, B. Eichler, S. Hübener, E. A. Sokol, A. Türler, A. V. Yeremin, G. V. Buklanov, M. L. Chelnokov, V. I. Chepigin, V. A. Gorshkov, A. V. Gulyaev, V. Ya. Lebedov, O.N. Malyshev, A. G. Popeko, S. Soverna, Z. Szeglowski, S. N. Timokhin, S. P. Tretyakova, V. M. Vasko, M. G. Itkis;
  "Chemical identification and properties of element 112"
  Radiochim. Acta, 91, 433-439, (2003); doi:10.1524/ract.91.8.433.20010.
• H. W. Gäggeler, W. Büchle, Ch. E. Düllmann, R. Dressler, K. Eberhardt, B. Eichler, R. Eichler, C .M. Folden, T. N. Ginter, F. Glaus, K. E. Gregorich, F. Haenssler, D.C. Hoffman, E. Jäger, D. T. Jost, U. W. Kirbach, J. V. Kratz, H. Nitsche, J. B. Patin, V. Peshina, D. Piguet, Z. Qin, U. Rieth, M. Schädel, E. Schimpf, B. Schausten, S. Soverna, R. Sudowe, P. Thörle, N. Trautmann, A. Türler, A. Vahle, P. A. Wilk, G. Wirth, A. B. Yakkushev, A. von Zweidorf;
  "Chemical and nuclear studies of hassium and element 112"
  Nucl. Phys., A734, 208-212, (2004); doi:10.1016/j.nuclphysa.2004.01.036.