First Observation of the Four-Proton Unbound Nucleus 18Mg

Jin, Y.; Niu, C. Y.; Brown, K. W.; Li, Z. H.; Hua, H.; Anthony, A. K.; Barney, J.; Charity, R. J.; Crosby, J.; Dell’Aquila, D.; Elson, J. M.; Estee, J.; Ghazali, M.; Jhang, G.; Li, J. G.; Lynch, W. G.; Michel, N.; Sobotka, L. G.; Sweany, S.; Teh, F. C. E.; Thomas, A.; Tsang, C. Y.; Tsang, M. B.; Wang, S. M.; Wu, H. Y.; Yuan, C.  X.; Zhu, K.

doi:10.1103/physrevlett.127.262502

First Observation of the Four-Proton Unbound Nucleus ¹⁸Mg

Journal Article · Wed Dec 22 00:00:00 EST 2021 · Physical Review Letters

DOI:https://doi.org/10.1103/physrevlett.127.262502· OSTI ID:1837749

^[1]; Niu, C. Y. ^[2]; Brown, K. W. ^[2]; Li, Z. H. ^[3]; Hua, H. ^[3]; Anthony, A. K. ^[2]; Barney, J. ^[2]; Charity, R. J. ^[4]; Crosby, J. ^[2]; Dell’Aquila, D. ^[2]; Elson, J. M. ^[4]; Estee, J. ^[2]; Ghazali, M. ^[2]; Jhang, G. ^[2]; Li, J. G. ^[5]; Lynch, W. G. ^[2]; Michel, N. ^[6]; Sobotka, L. G. ^[4]; Sweany, S. ^[2]; Teh, F. C. E. ^[2] more »

Peking Univ., Beijing (China); Washington University in St. Louis
Michigan State Univ., East Lansing, MI (United States)
Peking Univ., Beijing (China)
Washington Univ., St. Louis, MO (United States)
Peking Univ., Beijing (China); Chinese Academy of Sciences, Lanzhou (China); Univ. of Chinese Academy of Sciences, Beijing (China)
Chinese Academy of Sciences, Lanzhou (China); Univ. of Chinese Academy of Sciences, Beijing (China)
Fudan Univ., Shanghai (China); Michigan State Univ., East Lansing, MI (United States)
Sun Yat-Sen Univ., Zhuhai (China)

¹⁸Mg was observed, for the first time, by the invariant-mass reconstruction of ¹⁴O + 4p events. The ground-state decay energy and width are E_T = 4.865(34) MeV and Γ = 115(100) keV, respectively. The observed momentum correlations between the five particles are consistent with two sequential steps of prompt 2p decay passing through the ground state of ¹⁶Ne. The invariant-mass spectrum also provides evidence for an excited state at an excitation energy of 1.84(14) MeV, which is likely the first excited 2⁺ state. As this energy exceeds that for the 2⁺ state in ²⁰Mg, this observation provides an argument for the demise of the N = 8 shell closure in nuclei far from stability. Furthermore, in open systems this classical argument for shell strength is compromised by Thomas-Ehrman shifts.

View Accepted Manuscript (DOE)

Research Organization:: Washington Univ., St. Louis, MO (United States)

Sponsoring Organization:: USDOE Office of Science (SC), Nuclear Physics (NP)

Grant/Contract Number:: FG02-87ER40316

OSTI ID:: 1837749

Journal Information:: Physical Review Letters, Journal Name: Physical Review Letters Journal Issue: 26 Vol. 127; ISSN 0031-9007

Publisher:: American Physical Society (APS)Copyright Statement

Country of Publication:: United States

Language:: English

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