Observation of three-proton-decaying resonant states in 21Al
The structure of the proton-unbound nucleus Al 21 has been studied via proton transfer from a Be 9 target to a Mg 20 beam at E / A = 103 MeV. Three resonant states in Al 21 are identified by the invariant-mass reconstruction of Ne 18 + 3 p events. The decay-energy spectra for the two subsystems of Al 21 , i.e. Ne 18 + 1 p and Ne 18 + 2 p , indicate that the observed resonant state with the lowest energy has decay branches consisting of three sequential steps of one-proton decay. Based on the ab initio and the distorted-wave Born approximation (DWBA) calculations, this resonant state at E ⁎ = 6.09(11) MeV likely has a spin-parity of ( 1 / 2 + - 7 / 2 + ) . Meanwhile, the possibility that the observed resonant peak represents an admixture of several states cannot be ruled out. The good isospin-symmetry of the low-lying states with d 5 / 2 , d 3 / 2 configurations in the Al 21 - O 21 pair and the ab initio calculations indicate weak configuration mixing between the s - and d -orbital components. The systematics of experimental energy differences between the 5 / 2 + ground state and lowest-lying 3 / 2 + excited state for isotopes (isotones) of Z ( N ) = 13 suggest a likely semimagic nature of Al 21 .
Authors
- G. Jhang (ORCID: https://orcid.org/0000-0001-8664-3434)
- Thomas Allmendinger (ORCID: https://orcid.org/0000-0002-3340-3063)
- J. Barney (ORCID: https://orcid.org/0000-0002-8687-1290)
- S.M. Wang
- K. W. Brown (ORCID: https://orcid.org/0000-0003-1923-3595)
- Cenxi Yuan (ORCID: https://orcid.org/0000-0002-3495-3614)
- S. Sweany
- F. C. E. Teh (ORCID: https://orcid.org/0000-0002-8315-4317)
- Yi Jin (ORCID: https://orcid.org/0000-0002-0682-4313)
- W. G. Lynch (ORCID: https://orcid.org/0000-0003-4503-176X)
- M. B. Tsang (ORCID: https://orcid.org/0000-0002-4251-833X)
- H. y. Wu (ORCID: https://orcid.org/0000-0001-5928-195X)
- A. Anthony (ORCID: https://orcid.org/0000-0002-3220-7474)
- C. Y. Niu (ORCID: https://orcid.org/0009-0004-5765-4694)
- J.G. Li
- J. Estee
- C. Y. Tsang (ORCID: https://orcid.org/0000-0002-3617-1579)
- J. M. Elson (ORCID: https://orcid.org/0000-0001-7292-2088)
- H. Hua
- N. Michel (ORCID: https://orcid.org/0000-0003-4214-8620)
- R. J. Charity (ORCID: https://orcid.org/0000-0003-3020-4998)
- D. Dell’Aquila (ORCID: https://orcid.org/0000-0001-5895-0664)
- Zhen Li (ORCID: https://orcid.org/0000-0003-2786-7272)
- Kejun Zhu (ORCID: https://orcid.org/0000-0002-5473-235X)
- L.G. Sobotka
- Liufang Ni (ORCID: https://orcid.org/0009-0000-5589-9955)
Institutions
- Chinese Academy of Sciences (CN)
- Peking University (CN)
- Washington University in St. Louis (US)
- Institute of Modern Physics (CN)
- University of Chinese Academy of Sciences (CN)
- State Key Laboratory of Nuclear Physics and Technology
- Michigan State University (US)
Publication Details
- Journal
- Physics Letters B
- Published
- 2025-06-13
- DOI
- https://doi.org/10.1016/j.physletb.2025.139660
- Citations
- 1
- Primary Topic
- Nuclear physics research studies
- Type
- article
- Field-Weighted Citation Impact
- 1.87
Funders
- National Science Foundation
- National Natural Science Foundation of China
- Ministry of Science and Technology of the People's Republic of China
- Office of Science
- Major Projects of Guangdong Education Department for Foundation Research and Applied Research
- State Key Laboratory of Nuclear Physics and Technology, Peking University