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Is Seniority a Partial Dynamic Symmetry in the First $��g_{9/2}$ Shell?
- Publication Year :
- 2017
- Publisher :
- arXiv, 2017.
-
Abstract
- The low-lying structures of the midshell $��g_{9/2}$ Ni isotopes $^{72}$Ni and $^{74}$Ni have been investigated at the RIBF facility in RIKEN within the EURICA collaboration. Previously unobserved low-lying states were accessed for the first time following $��$ decay of the mother nuclei $^{72}$Co and $^{74}$Co. As a result, we provide a complete picture in terms of the seniority scheme up to the first $(8^+)$ levels for both nuclei. The experimental results are compared to shell-model calculations in order to define to what extent the seniority quantum number is preserved in the first neutron $g_{9/2}$ shell. We find that the disappearance of the seniority isomerism in the $(8^+_1)$ states can be explained by a lowering of the seniority-four $(6^+)$ levels as predicted years ago. For $^{74}$Ni, the internal de-excitation pattern of the newly observed $(6^+_2)$ state supports a restoration of the normal seniority ordering up to spin $J=4$. This property, unexplained by the shell-model calculations, is in agreement with a dominance of the single-particle spherical regime near $^{78}$Ni.
- Subjects :
- Nuclear Theory (nucl-th)
FOS: Physical sciences
Nuclear Experiment (nucl-ex)
Subjects
Details
- Database :
- OpenAIRE
- Accession number :
- edsair.doi...........06d7d7c8198fdede3003d49d91908221
- Full Text :
- https://doi.org/10.48550/arxiv.1710.11207