Spontaneous-fission decay properties and production cross-sections for the neutron-deficient nobelium isotopes formed in the 44,48Ca+204,206,208Pb reactions

Heavy-ion fusion reactions 48Ca+204Pb and 44Ca+208Pb leading to the same compound nucleus 252No* were run in attempts to produce new neutron-deficient spontaneous-fission isotopes of 249,250No 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 of 251-255No formed in the heavy-ion fusion reactions 48Ca+206Pb and 48Ca+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. (orig.)