Chen Z Q, Li Z H, Hua H, Watanabe H, Yuan C X, Zhang S Q, Lorusso G, Nishimura S, Baba H, Browne F, Benzoni G, Chae K Y, Crespi F C L, Doornenbal P, Fukuda N, Gey G, Gernhäuser R, Inabe N, Isobe T, Jiang D X, Jungclaus A, Jung H S, Jin Y, Kameda D, Kim G D, Kim Y K, Kojouharov I, Kondev F G, Kubo T, Kurz N, Kwon Y K, Li X Q, Lou J L, Lane G J, Li C G, Luo D W, Montaner-Pizá A, Moschner K, Niu C Y, Naqvi F, Niikura M, Nishibata H, Odahara A, Orlandi R, Patel Z, Podolyák Zs, Sumikama T, Söderström P-A, Sakurai H, Schaffner H, Simpson G S, Steiger K, Suzuki H, Taprogge J, Takeda H, Vajta Zs, Wang H K, Wu J, Wendt A, Wang C G, Wu H Y, Wang X, Wu C G, Xu C, Xu Z Y, Yagi A, Ye Y L, Yoshinaga K
School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China.
IRCNPC, School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191, China.
Phys Rev Lett. 2019 May 31;122(21):212502. doi: 10.1103/PhysRevLett.122.212502.
The β-delayed γ-ray spectroscopy of neutron-rich ^{123,125}Ag isotopes is investigated at the Radioactive Isotope Beam Factory of RIKEN, and the long-predicted 1/2^{-} β-emitting isomers in ^{123,125}Ag 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 ^{123,125}Ag. 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 ^{123}Ag can be well interpreted in terms of the monopole shift of the π1g_{9/2} orbitals mainly caused by the increasing occupation of ν1h_{11/2} orbitals.
在日本理化学研究所的放射性同位素束工厂对富中子的(^{123,125}Ag)同位素进行了β延迟γ射线光谱研究，并首次鉴定出长期预测的(^{123,125}Ag)中(1/2^-)β发射异构体。基于新的实验结果，在(N = 78)的(Ag)同位素中，最低(9/2^+)和(1/2^-)能级之间的能量间距系统趋势得到扩展，为(Ag)中朝向(N = 82)的(Z = 40)子壳层间隙减小提供了明确信号。采用最先进的(V_{MU})加(M3Y)自旋轨道相互作用的壳模型计算，对(^{123,125}Ag)中的低激发态给出了令人满意的描述。发现张量力在(Z = 40)子壳层间隙大小的演变中起关键作用。观察到的(^{123}Ag)周围单粒子能级的反转可以用主要由(ν1h_{11/2})轨道占据增加引起的(π1g_{9/2})轨道的单极移位很好地解释。
