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

¹ RIKEN Nishina Center, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
² Research Center for Nuclear Physics, Osaka University, Ibaraki, Osaka 567-0047, Japan
³ Department of Physics, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8551, Japan
⁴ Center for Nuclear Study, University of Tokyo,RIKEN campus, Wako, Saitama 351-0198, Japan
⁵ Institute for Nuclear Research, H-4001 Debrecen, P.O. Box 51, Hungary
⁶ Department of Physics, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima, Tokyo 172-8501, Japan
⁷ Department of Physics, University of Hong Kong, Pokfulam Road, Hong Kong
⁸ School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
⁹ Department of Physics, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan
Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan

^* e-mail: wanghe@ribf.riken.jp

Published online: 16 May 2018

Abstract

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.