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Abstract |
The beta-delayed gamma-ray spectroscopy of neutron-rich Ag-123,Ag-325 isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN, and the long-predicted 1/2(-) beta-emitting isomers in Ag-123,Ag-325 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 V-MU plus M3Y spin-orbit interaction give a satisfactory description of the low-lying states in Ag-123,Ag-325. 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 Ag-123 can be well interpreted in terms of the monopole shift of the pi 1g(9/2) orbitals mainly caused by the increasing occupation of nu 1h(11/2) orbitals. |
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Address |
[Chen, Z. Q.; Li, Z. H.; Hua, H.; Zhang, S. Q.; Jiang, D. X.; Jin, Y.; Li, X. Q.; Lou, J. L.; Li, C. G.; Luo, D. W.; Niu, C. Y.; Wu, J.; Wang, C. G.; Wu, H. Y.; Wang, X.; Wu, C. G.; Xu, C.; Ye, Y. L.] Peking Univ, Sch Phys, Beijing 100871, Peoples R China, Email: zhli@pku.edu.cn; |
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