Search for new isotopes of element 112 by irradiation of 238U with 48Ca

The reaction Ca-48+U-238 was investigated at the recoil separator VASSILISSA at the Flerov Laboratory of Nuclear Reactions, JINR Dubna, in attempts to synthesize new isotopes of element 112. The experiments were performed at two beam energies resulting in excitation energies of the compound nucleus of 33 and 39 MeV. The collected beam dose was 3.5x10(18) and 2.2x10(18), respectively. Two spontaneous fission events were observed at the lower beam energy, which tentatively were assigned to the new neutron rich isotope (283)112 produced in the reaction U-238(Ca-48,3n)(283)112. The measured cross-section is (5.0 (+6.3)(-3.2)) pb and the half-life is (81 (+147)(-32)) s. No event was observed at the higher beam energy resulting in the upper cross-section limit of 7.3 pb.