1
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Jin Y, Niu CY, Brown KW, Li ZH, Hua H, Anthony AK, Barney J, Charity RJ, Crosby J, Dell'Aquila D, Elson JM, Estee J, Ghazali M, Jhang G, Li JG, Lynch WG, Michel N, Sobotka LG, Sweany S, Teh FCE, Thomas A, Tsang CY, Tsang MB, Wang SM, Wu HY, Yuan CX, Zhu K. First Observation of the Four-Proton Unbound Nucleus ^{18}Mg. PHYSICAL REVIEW LETTERS 2021; 127:262502. [PMID: 35029460 DOI: 10.1103/physrevlett.127.262502] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Revised: 10/18/2021] [Accepted: 11/16/2021] [Indexed: 06/14/2023]
Abstract
^{18}Mg was observed, for the first time, by the invariant-mass reconstruction of ^{14}O+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 ^{16}Ne. 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 ^{20}Mg, this observation provides an argument for the demise of the N=8 shell closure in nuclei far from stability. However, in open systems this classical argument for shell strength is compromised by Thomas-Ehrman shifts.
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Affiliation(s)
- Y Jin
- School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - C Y Niu
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - K W Brown
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA
| | - Z H Li
- School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - H Hua
- School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - A K Anthony
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - J Barney
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - R J Charity
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, USA
| | - J Crosby
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - D Dell'Aquila
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - J M Elson
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, USA
| | - J Estee
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - M Ghazali
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - G Jhang
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - J G Li
- School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - W G Lynch
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - N Michel
- Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
- School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing 100049, China
| | - L G Sobotka
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, USA
- Department of Physics, Washington University, St. Louis, Missouri 63130, USA
| | - S Sweany
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - F C E Teh
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - A Thomas
- Department of Chemistry, Washington University, St. Louis, Missouri 63130, USA
| | - C Y Tsang
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - M B Tsang
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
| | - S M Wang
- Institute of Modern Physics, Fudan University, Shanghai 200433, China
- FRIB Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
| | - H Y Wu
- School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871, China
| | - C X Yuan
- Sino-French Institute of Nuclear Engineering and Technology, Sun Yat-Sen University, Zhuhai 519082, China
| | - K Zhu
- National Superconducting Cyclotron Laboratory, Michigan State University, East Lansing, Michigan 48824, USA
- Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824, USA
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2
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Suzuki D, Iwasaki H, Beaumel D, Nalpas L, Pollacco E, Assié M, Baba H, Blumenfeld Y, De Séréville N, Drouart A, Franchoo S, Gillibert A, Guillot J, Hammache F, Keeley N, Lapoux V, Maréchal F, Michimasa S, Mougeot X, Mukha I, Okamura H, Otsu H, Ramus A, Roussel-Chomaz P, Sakurai H, Scarpaci JA, Sorlin O, Stefan I, Takechi M. Breakdown of the Z=8 shell closure in unbound 12O and its mirror symmetry. PHYSICAL REVIEW LETTERS 2009; 103:152503. [PMID: 19905630 DOI: 10.1103/physrevlett.103.152503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Indexed: 05/28/2023]
Abstract
An excited state in the proton-rich unbound nucleus 12O was identified at 1.8(4) MeV via missing-mass spectroscopy with the 14O(p,t) reaction at 51 AMeV. The spin-parity of the state was determined to be 0+ or 2+ by comparing the measured differential cross sections with distorted-wave calculations. The lowered location of the excited state in 12O indicates the breakdown of the major shell closure at Z=8 near the proton drip line. This demonstrates the persistence of mirror symmetry in the disappearance of the magic number 8 between 12O and its mirror partner 12Be.
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Affiliation(s)
- D Suzuki
- Department of Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo, Tokyo 113-0033, Japan
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3
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Giovinazzo J, Blank B, Borcea C, Canchel G, Dalouzy JC, Demonchy CE, de Oliveira Santos F, Dossat C, Grévy S, Hay L, Huikari J, Leblanc S, Matea I, Pedroza JL, Perrot L, Pibernat J, Serani L, Stodel C, Thomas JC. First direct observation of two protons in the decay of 45Fe with a time-projection chamber. PHYSICAL REVIEW LETTERS 2007; 99:102501. [PMID: 17930383 DOI: 10.1103/physrevlett.99.102501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2007] [Indexed: 05/25/2023]
Abstract
The decay of the ground-state two-proton emitter 45Fe was studied with a time-projection chamber and the emission of two protons was unambiguously identified. The total decay energy and the half-life measured in this work agree with the results from previous experiments. The present result constitutes the first direct observation of the individual protons in the two-proton decay of a long-lived ground-state emitter. In parallel, we identified for the first time directly two-proton emission from 43Cr, a known beta-delayed two-proton emitter. The technique developed in the present work opens the way to a detailed study of the mechanism of ground state as well as beta-delayed two-proton radioactivity.
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Affiliation(s)
- J Giovinazzo
- Centre d'Etudes Nucléaires de Bordeaux Gradignan-Université Bordeaux 1-UMR 5797 CNRS/IN2P3, Chemin du Solarium, BP 120, F-33175 Gradignan Cedex, France
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4
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Mukha I, Roeckl E, Batist L, Blazhev A, Döring J, Grawe H, Grigorenko L, Huyse M, Janas Z, Kirchner R, La Commara M, Mazzocchi C, Tabor SL, Van Duppen P. Proton-proton correlations observed in two-proton radioactivity of 94Ag. Nature 2006; 439:298-302. [PMID: 16421564 DOI: 10.1038/nature04453] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2005] [Accepted: 11/21/2005] [Indexed: 11/09/2022]
Abstract
The stability and spontaneous decay of naturally occurring atomic nuclei have been much studied ever since Becquerel discovered natural radioactivity in 1896. In 1960, proton-rich nuclei with an odd or an even atomic number Z were predicted to decay through one- and two-proton radioactivity, respectively. The experimental observation of one-proton radioactivity was first reported in 1982, and two-proton radioactivity has now also been detected by experimentally studying the decay properties of 45Fe (refs 3, 4) and 54Zn (ref. 5). Here we report proton-proton correlations observed during the radioactive decay of a spinning long-lived state of the lightest known isotope of silver, 94Ag, which is known to undergo one-proton decay. We infer from these correlations that the long-lived state must also decay through simultaneous two-proton emission, making 94Ag the first nucleus to exhibit one- as well as two-proton radioactivity. We attribute the two-proton emission behaviour and the unexpectedly large probability for this decay mechanism to a very large deformation of the parent nucleus into a prolate (cigar-like) shape, which facilitates emission of protons either from the same or from opposite ends of the 'cigar'.
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Affiliation(s)
- Ivan Mukha
- Gesellschaft für Schwerionenforschung, D-64291 Darmstadt, Germany.
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8
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Oliveira JM, Lepine-Szily A, Bohlen HG, Ostrowski AN, Lichtenthaler R, Laird AM, Lima GF, Maunoury L, Roussel-Chomaz P, Savajols H, Trinder W, Villari AC. Observation of the 11N ground state. PHYSICAL REVIEW LETTERS 2000; 84:4056-4059. [PMID: 10990609 DOI: 10.1103/physrevlett.84.4056] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/1999] [Indexed: 05/23/2023]
Abstract
The ground state of the proton-rich, unbound nucleus 11N was observed, together with six excited states using the multinucleon transfer reaction 10B(14N,13B)11N at 30A MeV incident energy at Grand Accelerateur National d'Ions Lourds. Levels of 11N are observed as well defined resonances in the spectrum of the 13B ejectiles. They are localized at 1.63(5), 2.16(5), 3.06(8), 3.61(5), 4.33(5), 5.98(10), and 6.54(10) MeV above the 10C+p threshold. The ground-state resonance has a mass excess of 24.618(50) MeV; the experimental width is smaller than theoretical predictions.
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Affiliation(s)
- JM Oliveira
- IFUSP-Universidade de Sao Paulo, CP 66318, 05389-970 Sao Paulo, Brazil and CEBES-Centro de Ciencias Exatas, Biologicas e da Saude, Universidade de Sorocaba, Sorocaba, Brazil
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