2023

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.

The excited states of N=44 74Zn were investigated via γ-ray spectroscopy following 74Cu β decay. By exploiting γ−γ angular correlation analysis, the 2+2, 3+1, 0+2, and 2+3 states in 74Zn 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 74Zn 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.