Mass, Spectroscopy, and Two-Neutron Decay of Be 16

B. Monteagudo, F. M. Marque S, J. Gibelin, N. A. Orr, A. Corsi, Y. Kubota, J. Casal, J. Go Mez-Camacho, G. Authelet, H. Baba, C. Caesar, D. Calvet, A. Delbart, M. Dozono, J. Feng, F. Flavigny, J. M. Gheller, A. Giganon, A. Gillibert, K. HasegawaT. Isobe, Y. Kanaya, S. Kawakami, Y. Kiyokawa, M. Kobayashi, N. Kobayashi, T. Kobayashi, Y. Kondo, Z. Korkulu, S. Koyama, V. Lapoux, Y. Maeda, T. Motobayashi, T. Miyazaki, T. Nakamura, N. Nakatsuka, Y. Nishio, A. Obertelli, A. Ohkura, S. Ota, H. Otsu, T. Ozaki, V. Panin, S. Paschalis, E. C. Pollacco, S. Reichert, J. Y. Rousse, A. T. Saito, S. Sakaguchi, M. Sako, C. Santamaria, M. Sasano, H. Sato, M. Shikata, Y. Shimizu, Y. Shindo, L. Stuhl, T. Sumikama, M. Tabata, Y. Togano, J. Tsubota, T. Uesaka, J. Yasuda, K. Yoneda, J. Zenihiro

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The structure and decay of the most neutron-rich beryllium isotope, Be16, has been investigated following proton knockout from a high-energy B17 beam. Two relatively narrow resonances were observed for the first time, with energies of 0.84(3) and 2.15(5) MeV above the two-neutron decay threshold and widths of 0.32(8) and 0.95(15) MeV, respectively. These were assigned to be the ground (Jπ=0+) and first excited (2+) state, with Ex=1.31(6) MeV. The mass excess of Be16 was thus deduced to be 56.93(13) MeV, some 0.5 MeV more bound than the only previous measurement. Both states were observed to decay by direct two-neutron emission. Calculations incorporating the evolution of the wave function during the decay as a genuine three-body process reproduced the principal characteristics of the neutron-neutron energy spectra for both levels, indicating that the ground state exhibits a strong spatially compact dineutron component, while the 2+ level presents a far more diffuse neutron-neutron distribution.

Original languageEnglish
Article number082501
Number of pages6
JournalPhysical Review Letters
Issue number8
Publication statusPublished - 23 Feb 2024

Bibliographical note

Funding Information:
The authors wish to extend their thanks to the accelerator staff of the RIKEN Nishina Center for their efforts in delivering the intense beam. J. G., F. M. M., and N. A. O. acknowledge partial support from the Franco-Japanese LIA-International Associated Laboratory for Nuclear Structure Problems as well as the French ANR-14-CE33-0022-02 EXPAND. J. C. acknowledges financial support by the European Union’s Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement No. 101023609, by MCIN/AEI under I+D+i Project No. PID2020–114687 GB-I00, and by the Consejería de Economía, Conocimiento, Empresas y Universidad, Junta de Andalucía (Spain) and “ERDF-A Way of Making Europe” under PAIDI 2020 project No. P20_01247. J. G. C. is supported by MCIN/AEI under I+D+i Project No. PID2021-123879OB-C21. This work was also supported in part by JSPS KAKENHI Grants No. 24740154 and No. 16H02179, MEXT KAKENHI Grants No. 24105005 and No. 18H05404, the WCU (R32-2008-000-10155-0), the GPF (NRF-2011-0006492) programs of the NRF Korea, the HIC for FAIR, the CUSTIPEN (China-U.S. Theory Institute for Physics with Exotic Nuclei) funded by the U.S. Department of Energy, Office of Science under Grant No. DE-SC0009971, the Office of Nuclear Physics under Awards No. DE-SC0013365 (MSU) and No. DE-SC0018083 (NUCLEI SciDAC-4 Collaboration), and the European Research Council through the ERC Starting Grant No. MINOS-258567.

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