Proton Shell Evolution below Sn 132: First Measurement of Low-Lying β -Emitting Isomers in Ag 123,125

  • Z. Q. Chen
  • , Z. H. Li
  • , H. Hua
  • , H. Watanabe
  • , C. X. Yuan
  • , S. Q. Zhang
  • , G. Lorusso
  • , S. Nishimura
  • , H. Baba
  • , F. Browne
  • , G. Benzoni
  • , K. Y. Chae
  • , F. C.L. Crespi
  • , P. Doornenbal
  • , N. Fukuda
  • , G. Gey
  • , R. Gernhäuser
  • , N. Inabe
  • , T. Isobe
  • , D. X. Jiang
  • A. Jungclaus, H. S. Jung, Y. Jin, D. Kameda, G. D. Kim, Y. K. Kim, I. Kojouharov, F. G. Kondev, T. Kubo, N. Kurz, Y. K. Kwon, X. Q. Li, J. L. Lou, G. J. Lane, C. G. Li, D. W. Luo, A. Montaner-Pizá, K. Moschner, C. Y. Niu, F. Naqvi, M. Niikura, H. Nishibata, A. Odahara, R. Orlandi, Z. Patel, Zs Podolyák, T. Sumikama, P. A. Söderström, H. Sakurai, H. Schaffner, G. S. Simpson, K. Steiger, H. Suzuki, J. Taprogge, H. Takeda, Zs Vajta, H. K. Wang, J. Wu, A. Wendt, C. G. Wang, H. Y. Wu, X. Wang, C. G. Wu, C. Xu, Z. Y. Xu, A. Yagi, Y. L. Ye, K. Yoshinaga

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27 Scopus citations

Abstract

The β-delayed γ-ray spectroscopy of neutron-rich Ag123,125 isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN, and the long-predicted 1/2- β-emitting isomers in Ag123,125 are identified for the first time. With the new experimental results, the systematic trend of energy spacing between the lowest 9/2+ and 1/2- levels is extended in Ag isotopes up to N=78, providing a clear signal for the reduction of the Z=40 subshell gap in Ag towards N=82. Shell-model calculations with the state-of-the-art VMU plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in Ag123,125. The tensor force is found to play a crucial role in the evolution of the size of the Z=40 subshell gap. The observed inversion of the single-particle levels around Ag123 can be well interpreted in terms of the monopole shift of the π1g9/2 orbitals mainly caused by the increasing occupation of ν1h11/2 orbitals.

Original languageEnglish
Article number212502
JournalPhysical Review Letters
Volume122
Issue number21
DOIs
StatePublished - 28 May 2019

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