Is Seniority a Partial Dynamic Symmetry in the First $\nu g_{9/2}$ Shell?

Abstract

The low-lying structures of the midshell $\nu g_{9/2}$ 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 $\beta$ 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.

References in corpus (15)

• Identification and Separation of Radioactive Isotope Beams by the BigRIPS Separator at the RIKEN RI Beam Factory
• Shell-model calculations and realistic effective interactions
• Novel shape evolution in exotic Ni isotopes and configuration-dependent shell structure
• New T=1 effective interactions for the f5/2 p3/2 p1/2 g9/2 model space; Implications for valence-mirror symmetry and seniority isomers
• Effective shell-model hamiltonians from realistic nucleon-nucleon potentials within a perturbative approach
• Partial Dynamical Symmetry in Deformed Nuclei
• Partial conservation of seniority and nuclear isomerism
• Seniority conservation and seniority violation in the g_{9/2} shell
• Partial conservation of seniority in $j=9/2$ shell: Analytic and numerical studies
• Realistic shell-model calculations for isotopic chains "north-east'' of 48Ca in the (N,Z) plane
• Seniority in quantum many-body systems. I. Identical particles in a single shell
• Energy expressions for n=3 and 4 systems in a single-j shell
• Simultaneous investigation of the $\mathbf{T}=1({\mathbf{J}}^{\pi }=0^{+})$ and $\mathbf{T}=0({\mathbf{J}}^{\pi }=9^{+})$ $\beta$ decays in ${}^{70}$Br
• Partial conservation of seniority and its unexpected influence on E2 transitions in $g_{9/2}$ nuclei
• Relations Between Coefficients of Fractional Parentage

Cited by in corpus (7)

• Segmented YSO scintillation detectors as a new $\beta$-implant detection tool for decay spectroscopy in fragmentation facilities
• Manifestation of the Berry phase in the atomic nucleus ${}^{213}$Pb
• Effects of one valence proton on seniority and angular momentum of neutrons in neutron-rich ${}^{122-131}$Sb${}_{51}$ isotopes
• Persistence of the $Z=28$ shell gap in $A=75$ isobars: Identification of a possible $(1/2^{-})$ $\mu$s isomer in ${}^{75}$Co and $\beta$ decay to ${}^{75}$Ni
• Seniority and $(\frac{9}{2}{)}^n$ configurations in neutron-rich Nickel isotopes
• Partial conservation of seniority in semi-magic nuclei
• Relation to a property of the angular momentum zero space of states of four fermions in an angular momentum $j=9/2$ shell unexpectedly found to be stationary for any rotationally invariant two-body interaction