Instituto de Estructura de la Materia, CSIC, E-28006 Madrid, Spain and Departamento de Física Teórica, Universidad Autónoma de Madrid, E-28049 Madrid, Spain and RIKEN Nishina Center, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198, Japan.
Instituto de Estructura de la Materia, CSIC, E-28006 Madrid, Spain.
Phys Rev Lett. 2014 Apr 4;112(13):132501. doi: 10.1103/PhysRevLett.112.132501. Epub 2014 Apr 1.
A low-lying state in 131In82, the one-proton hole nucleus with respect to double magic 132Sn, was observed by its γ decay to the Iπ=1/2- β-emitting isomer. We identify the new state at an excitation energy of Ex=1353 keV, which was populated both in the β decay of 131Cd83 and after β-delayed neutron emission from 132Cd84, as the previously unknown πp3/2 single-hole state with respect to the 132Sn core. Exploiting this crucial new experimental information, shell-model calculations were performed to study the structure of experimentally inaccessible N=82 isotones below 132Sn. The results evidence a surprising absence of proton subshell closures along the chain of N=82 isotones. The consequences of this finding for the evolution of the N=82 shell gap along the r-process path are discussed.
在 131In82 中，观察到一个相对于双幻数 132Sn 的具有一个质子空穴的低能级核，通过其 γ 衰变到 Iπ=1/2- β 发射同质异能态。我们将这个新的能级确定在激发能量 Ex=1353 keV，它在 131Cd83 的 β 衰变和 132Cd84 的 β 延迟中子发射后都有产生，这是之前未知的相对于 132Sn 核的 πp3/2 单空穴能级。利用这一关键的新实验信息，进行了壳模型计算，以研究实验上无法到达的 N=82 同位素链以下的 132Sn 同位素的结构。结果表明，在 N=82 同位素链上，质子子壳层的闭合出乎意料地不存在。讨论了这一发现对 r 过程路径上 N=82 壳隙演化的影响。
