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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]

Aiming at an increase in the identification ability and higher sensitivity in the experiments on the synthesis and study of the decay properties of superheavy nuclei, the separator VASSILISSA has been upgraded. After preparatory experiments, the experiment aiming at the synthesis of the isotope 283112 in the reaction 48Ca + 238U was performed. The obtained results on the decay mode, half-life and production cross-section are in agreement with those obtained in our first experiment. [Copyright &y& Elsevier]