Proton Shell Evolution below $^{132}\mathrm{Sn}$: First Measurement of Low-Lying $\beta$-Emitting Isomers in $^{123,125}\mathrm{Ag}$

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 (1, 2) , 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 (1) , 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

1 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
2 ILL - Institut Laue-Langevin

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.

Mots clés: Nuclear Physics

Domaines: Physique Nucléaire Expérimentale [nucl-ex]

Z.Q. Chen, Z.H. Li, H. Hua, H. Watanabe, C.X. Yuan, et al.. Proton Shell Evolution below $^{132}\mathrm{Sn}$: First Measurement of Low-Lying $\beta$-Emitting Isomers in $^{123,125}\mathrm{Ag}$. Physical Review Letters, 2019, 122 (21), pp.212502. ⟨10.1103/PhysRevLett.122.212502⟩. ⟨hal-02189124⟩