Direct Evidence for the νd512 Orbital in 69Ni: Implications for the N=40 Island of Inversion

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Ceulemans, A, Raabe, R, Nowacki, F, Alharbi, A, Ayatollahzadeh, H, Bennett, SA, Browne, F, Butler, PA ORCID: 0000-0001-6080-9205, Camaiani, A, Clarke, D et al (show 25 more authors) , Dolan, AJ, Eleme, Z, Everett, CTA, Flavigny, F, Fracassetti, S, Freeman, SJ, Gaffney, LP ORCID: 0000-0002-2938-3696, Georgiev, G, Goula, S, Heinz, A, Kawecka, A, Keatings, JM, Labiche, M, Lazarus, I, MacGregor, PT, Managlia, MV, Ojala, J, Olaizola, B, Page, RD ORCID: 0009-0009-7062-711X, Patronis, N, Poleshchuk, O, Sanchez-Benitez, AM, Sharp, DK, Tornqvist, H and Youssef, A (2025) Direct Evidence for the νd512 Orbital in 69Ni: Implications for the N=40 Island of Inversion PHYSICAL REVIEW LETTERS, 135 (25). 252502-. ISSN 0031-9007, 1079-7114

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Abstract

Shape coexistence, a collective manifestation of nuclear structure, emerges from the underlying single-particle dynamics and is prominently observed in the region below Ni68. Theoretical studies have emphasized the key role of the νd5/2 orbital, the quadrupole partner of νg9/2, in driving deformation. However, experimental constraints on the location and properties of neutron orbitals in neutron-rich isotopes in this region remain scarce. In this Letter, the single-particle structure of Ni69 was investigated via the Ni68(d,p) reaction in inverse kinematics, performed at the ISOLDE Solenoidal Spectrometer at CERN. Several new excited states were observed, and comparisons with adiabatic distorted wave approximation (ADWA) calculations enabled ℓ-value assignments for the most strongly populated states. In particular, a state at 2.56 MeV is interpreted as the dominant fragment of the νd5/2 strength. The experimental findings are well reproduced by Large-Scale Shell Model calculations using a modified LNPS interaction with an increased νg9/2-νd5/2 energy gap. These results provide new insight into the structure of Ni69 and underscore the crucial role of the νd5/2 orbital in the onset of collectivity at the N=40 island of inversion.

Item Type:	Article
Uncontrolled Keywords:	ISS Collaboration, ISOLDE Collaboration
Divisions:	Faculty of Science & Engineering Faculty of Science & Engineering > School of Physical Sciences Faculty of Science & Engineering > School of Physical Sciences > Physics
Depositing User:	Symplectic Admin
Date Deposited:	06 Jan 2026 09:14
Last Modified:	16 Jun 2026 20:12
DOI:	10.1103/tdfs-5qzw
Open Access URL:	https://journals.aps.org/prl/abstract/10.1103/tdfs...
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3196415
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