0000000000006226
AUTHOR
K. Nishio
Towards saturation of the electron-capture delayed fission probability : The new isotopes 240Es and 236Bk
The new neutron-deficient nuclei 240Es and 236Bk were synthesised at the gas-filled recoil separator RITU. They were identified by their radioactive decay chains starting from 240Es produced in the fusion–evaporation reaction 209Bi(34S,3n)240Es. Half-lives of 6(2) sand 22+13−6swere obtained for 240Es and 236Bk, respectively. Two groups of αparticles with energies Eα=8.19(3) MeVand 8.09(3) MeVwere unambiguously assigned to 240Es. Electron-capture delayed fission branches with probabilities of 0.16(6)and 0.04(2)were measured for 240Es and 236Bk, respectively. These new data show a continuation of the exponential increase of ECDF probabilities in more neutron-deficient isotopes. peerReviewed
Decay studies of new isomeric states in 255No
The decay of excited states in 255No was investigated by applying the evaporation-residue–conversion-electron correlation technique. Two new isomeric states were observed in 255No together with the previously known one. Excitation energies of the isomeric states were estimated based on the energies of conversion electrons and γ rays from correlation chains. These results were in accord with theoretical calculations based on the mean-field models. A tentative decay scheme of isomeric states in 255No is proposed, and their Nilsson configurations are discussed. The energy decrease of the 11/2−[725] Nilsson level for heavy N=153 isotones as a function of increasing proton number is confirmed. p…
Studies of SHE at SHIP
An overview of present experimental investigation of superheavy elements is given. The data are compared with theoretical descriptions. Results are reported from an experiment to confirm production of element 112 isotopes in irradiation of 238UF4 with 48Ca. One spontaneous fission event was measured, which agrees with three events of previously measured data which had been assigned to the decay of 283112. However, more experimental work is needed in order to obtain an independent and unambiguous confirmation of previous results.
Beta-delayed fission of 186, 188Bi isotopes
By using the technique of correlating implanted evaporation residues and their subsequent fission decay, β-delayed fission (βDF) of 186Bi has been identified for the first time and βDF of 188Bi has been unambiguously confirmed. The experiments were performed at the velocity filter SHIP (GSI, Darmstadt). The βDF probabilities for both nuclides were qualitatively estimated, and, in particular indications for a large value in the case of 186Bi are regarded. peerReviewed
Population of nuclides with Z≥98 in multi-nucleon transfer reactions of 48Ca + 248Cm
The results for nuclei above curium, produced in multi-nucleon transfer reactions of 48Ca + 248Cm at the velocity filter SHIP of GSI Darmstadt, are presented. Spontaneous fission and α-activities have been used to study the population of nuclei with lifetimes ranging from few milliseconds to several days. We observed several, relatively neutron-rich isotopes with atomic numbers Z≥98; among them a weak 224 millisecond activity which we tentatively attributed to 260No. The measured cross-sections of the observed nuclei give hope that multi-nucleon transfer reactions are a way to reach new neutron-rich heavy and superheavy nuclei, which are not accessible in other reactions. We compare our res…