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Heavy-ion fusion reactions48Ca +204Pb and44Ca +208Pb leading to the same compound nucleus252No* were run in attempts to produce new neutron-deficient spontaneous-fission isotopes of249,250No using the electrostatic separator VASSILISSA. Production cross-sections for the spontaneous-fission activities with the half-lives 5.6 and 54 μs observed in these reactions are compared with the measured ones for the well-known isotopes of251 - 255No formed in the heavy-ion fusion reactions48Ca +206Pb and48Ca +208Pb. The obtained excitation functions for the reaction products formed after the evaporation of 1-4 neutrons from the corresponding compound No nuclei have been compared with similar data obtained earlier and results of statistical model calculations. [ABSTRACT FROM AUTHOR]

The reaction 48Ca+238U 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 3.5 × 1018 and 2.2 × 1018, respectively. Two spontaneous fission events were observed at the lower beam energy, which tentatively were assigned to the new neutron rich isotope 283112 produced in the reaction 238U(48Ca,3n)283112. 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. [ABSTRACT FROM AUTHOR]