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.
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. Gernhauser, 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-Piza, K. Moschner, C.Y. Niu, F. Naqvi, M. Niikura, H. Nishibata, A. Odahara, R. Orlandi, Z. Patel, Z. Podolyak, T. Sumikama, P.-. Soderstrom, H. Sakurai, H. Schaffner, G.S. Simpson, K. Steiger, H. Suzuki, J. Taprogge, H. Takeda, Z. 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. - In: PHYSICAL REVIEW LETTERS. - ISSN 0031-9007. - 122:21(2019 May 28), pp. 212502.212502-1-212502.6.
Proton Shell Evolution below Sn 132: First Measurement of Low-Lying β -Emitting Isomers in Ag 123,125
F.C.L. Crespi;
2019
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.
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