First Evidence of Axial Shape Asymmetry and Configuration Coexistence in ^{74}Zn: Suggestion for a Northern Extension of the N=40 Island of Inversion

The excited states of N=44 ^{74}Zn were investigated via γ-ray spectroscopy following ^{74}Cu β decay. By exploiting γ-γ angular correlation analysis, the 2_{2}^{+}, 3_{1}^{+}, 0_{2}^{+}, and 2_{3}^{+} states in ^{74}Zn were firmly established. The γ-ray branching and E2/M1 mixing ratios for transit...

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Bibliographic Details
Published in:Physical review letters 2023-03, Vol.130 (12), p.122502-122502
Main Authors: Rocchini, M, Garrett, P E, Zielińska, M, Lenzi, S M, Dao, D D, Nowacki, F, Bildstein, V, MacLean, A D, Olaizola, B, Ahmed, Z T, Andreoiu, C, Babu, A, Ball, G C, Bhattacharjee, S S, Bidaman, H, Cheng, C, Coleman, R, Dillmann, I, Garnsworthy, A B, Gillespie, S, Griffin, C J, Grinyer, G F, Hackman, G, Hanley, M, Illana, A, Jones, S, Laffoley, A T, Leach, K G, Lubna, R S, McAfee, J, Natzke, C, Pannu, S, Paxman, C, Porzio, C, Radich, A J, Rajabali, M M, Sarazin, F, Schwarz, K, Shadrick, S, Sharma, S, Suh, J, Svensson, C E, Yates, D, Zidar, T
Format: Article
Language:English
Subjects:
Nuclear Experiment
Nuclear Theory
Physics
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Summary:The excited states of N=44 ^{74}Zn were investigated via γ-ray spectroscopy following ^{74}Cu β decay. By exploiting γ-γ angular correlation analysis, the 2_{2}^{+}, 3_{1}^{+}, 0_{2}^{+}, and 2_{3}^{+} states in ^{74}Zn were firmly established. The γ-ray branching and E2/M1 mixing ratios for transitions deexciting the 2_{2}^{+}, 3_{1}^{+}, and 2_{3}^{+} states were measured, allowing for the extraction of relative B(E2) values. In particular, the 2_{3}^{+}→0_{2}^{+} and 2_{3}^{+}→4_{1}^{+} transitions were observed for the first time. The results show excellent agreement with new microscopic large-scale shell-model calculations, and are discussed in terms of underlying shapes, as well as the role of neutron excitations across the N=40 gap. Enhanced axial shape asymmetry (triaxiality) is suggested to characterize ^{74}Zn in its ground state. Furthermore, an excited K=0 band with a significantly larger softness in its shape is identified. A shore of the N=40 "island of inversion" appears to manifest above Z=26, previously thought as its northern limit in the chart of the nuclides.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.130.122502