Mass, Spectroscopy, and Two-Neutron Decay of ^{16}Be

• Published in: Physical review letters Vol. 132; no. 8; p. 082501
• Main Authors: Monteagudo, B, Marqués, F M, Gibelin, J, Orr, N A, Corsi, A, Kubota, Y, Casal, J, Gómez-Camacho, J, Authelet, G, Baba, H, Caesar, C, Calvet, D, Delbart, A, Dozono, M, Feng, J, Flavigny, F, Gheller, J-M, Giganon, A, Gillibert, A, Hasegawa, K, Isobe, T, Kanaya, Y, Kawakami, S, Kim, D, Kiyokawa, Y, Kobayashi, M, Kobayashi, N, Kobayashi, T, Kondo, Y, Korkulu, Z, Koyama, S, Lapoux, V, Maeda, Y, Motobayashi, T, Miyazaki, T, Nakamura, T, Nakatsuka, N, Nishio, Y, Obertelli, A, Ohkura, A, Ota, S, Otsu, H, Ozaki, T, Panin, V, Paschalis, S, Pollacco, E C, Reichert, S, Rousse, J-Y, Saito, A T, Sakaguchi, S, Sako, M, Santamaria, C, Sasano, M, Sato, H, Shikata, M, Shimizu, Y, Shindo, Y, Stuhl, L, Sumikama, T, Sun, Y L, Tabata, M, Togano, Y, Tsubota, J, Uesaka, T, Yang, Z H, Yasuda, J, Yoneda, K, Zenihiro, J
• Format: Journal Article
• Language: English
• Published: United States 23.02.2024
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.132.082501

The structure and decay of the most neutron-rich beryllium isotope, ^{16}Be, has been investigated following proton knockout from a high-energy ^{17}B 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 (J^{π}=0^{+}) and first excited (2^{+}) state, with E_{x}=1.31(6)  MeV. The mass excess of ^{16}Be 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.