Nuclear structure study for the neutron-rich nuclei beyond 132Sn: In-beam gamma-ray spectroscopy of 136Sn and 132Cd

The neutron-rich nuclei 136Sn and 132Cd have been studied in the purpose of nuclear structure for the nuclei beyond the doubly-magic nucleus 132Sn. The 2+1 → 0+ gs transitions were identified for these two nuclei using in-beam γ-ray spectroscopy in coincidence with one- and two-proton removal reactions, respectively, at the RIKEN Radioactive Isotope Beam Factory. The 2+ 1 state in 136Sn is found to be similar to that for 134Sn indicating the seniority scheme may also hold for the heavy tin isotopes beyond N = 82. For 132Cd, the 2+ 1 state provides the first spectroscopic information in the even-even nuclei locating in the region “southeast” of 132Sn and the result is discussed in terms of proton-neutron configuration mixing. In both these two nuclei, it was found that the valence neutrons play an essential role in their low-lying excitations.

NEUTRON CORRELATIONS IN 6He VIEWED THROUGH NUCLEAR BREAK-UP

Nuclear break-up as a tool to study neutron correlations is investigated both theoretically and experimentally. First a time dependent theory going beyond mean field has been developed and shows that correlations between nucleons can be probed through nuclear break-up. Secondly, nuclear break-up of 6 He on 208 Pb target was studied at 20 A.MeV using a secondary beam of 6 He produced by the SPIRAL facility at GANIL. From the correlation function, a strong contribution of the di-neutron configuration of 6 He is found.

STUDY OF LIGHT UNSTABLE NUCLEI VIA DIRECT NUCLEAR REACTIONS

Sensitivity of the direct nuclear reaction to the exotic structure of the unstable nuclei is outlined. The transfer reaction induced by 6 He on a 9 Be target at 25 MeV/u is described. The theoretical analysis using CRC model supports the di-neutron configuration of the two valence neutrons in 6 He . Preliminary calculation for 17 Ne were introduced which indicates the advantage of using transfer reaction to clarify the s-wave or d-wave configuration of the valence protons.

Level structures in 180Hf from the β decay of 180Lu

Configuration assignments to the levels of 180Hf populated in the β decay of the 5.7 min ground state of 180Lu are derived based on the observed β-transition rates, calculated two-quasiparticle excitation energies, and the observed decay modes of the levels under consideration. Corroborative evidence is sought from the results of the other experimental investigations including (n, γ), (n, 2γ), (n, n′γ), and particle transfer reaction studies. Specifically the 1607.7 and 1742.7 keV levels are assigned the IπK = 4+4 and 5+4 {7/2[514] + 1/2[510]} two-neutron configuration, and the 1374.7 and 1609.7 keV levels are assigned the 4−4 and 5−5 {9/2[624] + 1/2[510]} two-neutron configuration.