Further evidence for shape coexistence in $^{79}$Zn$^{m}$ near doubly-magic $^{78}$Ni

L. Nies, L. Canete, D. D. Dao, S. Giraud, A. Kankainen, D. Lunney, F. Nowacki, B. Bastin, M. Stryjczyk, P. Ascher, K. Blaum, R. B. Cakirli, T. Eronen, P. Fischer, M. Flayol, V. Girard Alcindor, A. Herlert, A. Jokinen, A. Khanam, U. Köster, D. Lange, I. D. Moore, M. Müller, M. Mougeot, D. A. Nesterenko, H. Penttilä, C. Petrone, I. Pohjalainen, A. de Roubin, V. Rubchenya, Ch. Schweiger, L. Schweikhard, M. Vilen, J. Äystö
Nuclear Experiment, Nuclear Experiment (nucl-ex), Nuclear Theory (nucl-th)
2023-10-24 16:00:00
Isomers close to doubly-magic $^{78}_{28}$Ni$_{50}$ provide essential information on the shell evolution and shape coexistence near the ${Z=28}$ and ${N=50}$ double shell closure. We report the excitation energy measurement of the $1/2^{+}$ isomer in $^{79}_{30}$Zn$_{49}$ through independent high-precision mass measurements with the JYFLTRAP double Penning trap and with the ISOLTRAP Multi-Reflection Time-of-Flight Mass Spectrometer. We unambiguously place the $1/2^{+}$ isomer at 942(10) keV, slightly below the $5/2^+$ state at 983(3) keV. With the use of state-of-the-art shell-model diagonalizations, complemented with Discrete Non Orthogonal shell-model calculations which are used here the first time to interpret shape coexistence, we find low-lying deformed intruder states, similar to other ${N=49}$ isotones. The $1/2^{+}$ isomer is interpreted as the band-head of a low-lying deformed structure akin to a predicted low-lying deformed band in $^{80}$Zn, and points to shape coexistence in $^{79,80}$Zn similar to the one observed in $^{78}$Ni. The results make a strong case for confirming the claim of shape coexistence in this key region of the nuclear chart.
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