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An experimental study of 256Rf spontaneous fission following the fusion reaction of 50Ti+208Pb was performed using the velocity filter SHELS of the Flerov laboratory at JINR. The average number of neutrons of ν‾=4.30±0.17 and variance of σν2=3.2 from the prompt neutron multiplicity distribution were obtained. The alpha decay branching ratio of bα=0.003−0.003+0.005 and the half-life of T1/2=(6.7±0.2) ms of the isotope were determined. For the first time, our neutron detector system allowed us to extend investigation of the prompt neutron multiplicity study to the superheavy element region.

The analysis of fission events following the implantation of evaporation residues produced in the fusion reaction of 50Ti and 209Bi at different bombarding energies has revealed 5 millisecond decays, which are attributed to the spontaneous fission of proton-evaporation channels. The average cross sections for proton evaporation are found to be ∼100 and 10 times smaller than the largest neutron-evaporation channel cross section at the same excitation energy. These results suggest that the proton evaporation channel, albeit weak, may represent a realistic alternative to synthesize new, more neutron rich super heavy nuclei. Keywords: Fusion-evaporation reaction, Proton evaporation, Super heavy nuclei, Cross section