Study on the isomeric decay of neutron-rich isotope ⁶⁷Fe

Gamma-delayed spectroscopy measurements of 67Fe have been performed at RIKEN,Japan. The spectra from (p, 2p) and (p, pn) channels show a sharp peak at 367 keV. While the total isomer-yield spectrum presents clearly 2 peaks at 367 and 387 keV. The ratio of these two gammas’ intensity was determined to be equal to 0.126(3), in agreement with previous experiments. The origin of these two gammas could be from different isomers of 67Fe. The half-life (T1/2) of the isomer which decays to the 367 keV level was determined to be equal to 150(10) s, more than twice as long as from previous experiments.

QUEST FOR MAGICITY IN EXOTIC NUCLEI

Low-lying excitation properties of exotic nuclei in the vicinity of the canonical magic number 8 have been investigated through the level lifetime measurement on the neutron-rich isotope 13 B with N = 8 and the missing-mass spectroscopy on the proton unbound nucleus 12 O with Z = 8. The observed trends of the transition probabilities and level schemes have been discussed in comparison with the advanced shell model calculations, which points to the universality as well as the charge independence of the shell quenching phenomena far from stability.

BAND STRUCTURES IN 12Be: EXPERIMENTAL RESULTS

The structure of the neutron-rich isotope 12 Be has been studied using different transfer reactions, which populate distinct structures in 12 Be . This concerns two-neutron and three-neutron stripping reactions and two-proton pick-up reactions at incident energies of 15–20 MeV/u. Band structures of positive and negative parity are discussed.

SYNTHESIS OF HEAVIEST ELEMENTS (RESULTS AND PROSPECTS)

The formation and decay properties of the heaviest nuclei with Z = 112 - 116 and 118 were studied in the reactions 238 U , 242,244 Pu , 243 Am , 245,248 Cm and 249 Cf +48 Ca . The new nuclides mainly undergo sequential α-decay, which ends with spontaneous fission. The total time of decays ranges from 0.5 ms to about 1 day, depending on the proton and neutron numbers in the synthesized nuclei. The atomic number of the new elements 115 and 113 was confirmed also by an independent radiochemical experiment based on the identification of the neutron-rich isotope 268 Db (TSF ≈ 30 h ), the final product in the chain of α-decays of the odd–odd parent nucleus 288115. The comparison of the decay properties of 29 new nuclides with Z = 104 - 118 and N = 162 - 177 gives evidence for the decisive influence of the structure of superheavy nuclei on their stability with respect to different modes of radioactive decay. The investigations connected with the search for superheavy elements in Nature (cosmic rays) and prospects of superheavy element research are also presented.