Attempts to chemically investigate element 112

Two experiments aiming at the chemical investigation of element 112 produced in the heavy ion induced nuclear fusion reaction of Ca-48 with U-238 were performed at the Geselischaft fur Schwerionenforschung (GSI), Darmstadt, Germany. Both experiments were designed to determine the adsorption enthalpy of element 112 on a gold surface using a thermochromatography setup. The temperature range covered in the thermochromatography experiments allowed the adsorption of Hg at about 35 degrees C and of Rn at about - 180 degrees C. Reports from the Flerov Laboratory for Nuclear Reactions (FLNR), Dubna, Russia claim production of a 5-min spontaneous fission (SF) activity assigned to 2111 12 for the U-238 (Ca-48,3n) (283)112 reaction. Hence, Experiment I was designed to detect spontaneously fissioning (SF) isotopes of elernent 112 with half-lives (t(1/2)) longer than about 20 s. 11 high-energy events were detected. 7 events exhibit a deposlition pattern resembling a chromatographic peak in the vicinity of Rn deposition. However, the energy of the events observed in Experiment I was lower than expected for a SF-decay of (283)112. Therefore, these events could not be unambiguously attributed to the decay of (283)112. In contradiction with earlier publications newer reports from FLNR Dubna claim that (283)12 decays by a-particle ernission (E-alpha = 9.5 MeV) with t(1/2) = 4 s followed by a SF-decay of (279)Ds (t(1/2) = 0.2 s). Therefore, Experiment II was designed to be sensitive to both claimed decay properties of (283)112. However, during this experiment neither short alpha-SF correlations nor SF coincidences were detected. The conclusion is that (283)112 was not unambiguously detected, neither in Experiment I nor in Experiment II.