Abstract
The low-lying structures of the midshell νg9/2 Ni isotopes 72Ni and 74Ni 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 β decay of the mother nuclei 72Co and 74Co. 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 g9/2 shell. We find that the disappearance of the seniority isomerism in the (81 +) states can be explained by a lowering of the seniority-four (6+) levels as predicted years ago. For 74Ni, the internal de-excitation pattern of the newly observed (62 +) 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 78Ni.
Original language | English |
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Pages (from-to) | 706-712 |
Number of pages | 7 |
Journal | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics |
Volume | 781 |
DOIs | |
Publication status | Published - 10 Jun 2018 |