SPONTANEOUS FISSION OF $^{256}$Rf AND $^{250}$No — NEW EXPERIMENTAL DATA

In the last years we carried out several experiments aimed to investigate properties of short-lived SF isotopes. The neutron-deficient isotope 256Rf were produced in fusion-evaporation reactions using an 208Pb target and an intense 50Ti beam. Fusion-evaporation residues were separated by the SHELS separator (FLNR, Dubna) and implanted into a large-area double-sided silicon 48×48 strip detector surrounded by 3He-based neutron counters. The half-life and decay branching ratio of 256Rf is measured. The average number of neutrons per spontaneous fission of 256Rf is determined for the first time. Next we carried out an experiment aimed at investigating the properties of spontaneous fission of neutron deficient isotope 250No produced in the reaction with 48Cabeam and 204Pb-target. Earlier two spontaneous fission half-lives (t1/2 = 5.1±0.3 μs and t1/2 = 36±3 μs) originate from 250No were registered. The obtained excitation functions after the evaporation of 2 neutrons from the compound 252No nuclei have been compared with similar data obtained earlier. From the experimental data for the first time the average number of neutrons per spontaneous fission and TKE-spectra of fission fragments of both 250No activities was determined