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

摘要

The neutron-rich nuclei~(136)Sn and~(132)Cd have been studied in the purpose of nuclear structure for the nuclei beyond the doubly-magic nucleus~(132)Sn. 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~(136)Sn is found to be similar to that for~(134)Sn indicating the seniority scheme may also hold for the heavy tin isotopes beyond N = 82. For~(132)Cd, the 2~(+)_(1)state provides the first spectroscopic information in the even-even nuclei locating in the region “southeast” of~(132)Sn 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.