Speaker
Description
Isomers close to the doubly magic nucleus 78Ni (Z=28, N=50) provide essential information on the shell evolution and shape coexistence far from stability. We have performed high-precision mass measurements of isomeric states close to 78Ni with the JYFLTRAP double Penning trap mass spectrometer [1] at the Ion Guide Isotope Separator On-Line (IGISOL) facility. The existence of a long-lived isomeric state in 76Cu has been debated for a long time. We confirm the existence of such an isomeric state with an excitation energy Ex=64.8(25) keV [2]. Based on the ratio of detected ground- and isomeric-state ions as a function of time, we show that the isomer is the shorter-living state previously considered as the ground state of 76Cu. In addition to 76Cu, we measured the 1/2+ isomeric state of 79Zn. This isomer is known to be strongly deformed [3]. We place it unambiguously at 942(10) keV, slightly below the 5/2+ state at 983(3) keV. Using the state-of-the-art shell-model calculations, the 1/2+ isomer in 79Zn is interpreted as the bandhead of a low-lying deformed structure akin to a predicted low-lying deformed band in 80Zn. The results show the importance of high-precision mass measurements as pinning down the excitation energies of long-living isomeric states and give support for shape coexistence in the 78Ni region.
[1] T. Eronen et al., Eur. Phys. J. A 48, 46 (2012).
[2] L. Canete et al., Phys. Lett. B 853, 138663 (2024).
[3] X. F. Yang et al., Phys. Rev. Lett. 116, 182502 (2016).
[4] L. Nies, L. Canete et al., Phys. Rev. Lett. 131, 222503 (2023).
