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arXiv · 2407.19303

Magicity versus superfluidity around $^{28}$O viewed from the study of $^{30}$F

J. Kahlbow·T. Aumann·O. Sorlin·Y. Kondo·T. Nakamura·F. Nowacki·A. Revel·N. L. Achouri·H. Al Falou·L. Atar·H. Baba·K. Boretzky·C. Caesar·D. Calvet·H. Chae·N. Chiga·A. Corsi·F. Delaunay·A. Delbart·Q. Deshayes·Z. Dombradi·C. A. Douma·Z. Elekes·I. Gasparic·J. -M. Gheller·J. Gibelin·A. Gillibert·M. N. Harakeh·A. Hirayama·M. Holl·A. Horvat·A. Horvath·J. W. Hwang·T. Isobe·N. Kalantar-Nayestanaki·S. Kawase·S. Kim·K. Kisamori·T. Kobayashi·D. Körper·S. Koyama·I. Kuti·V. Lapoux·S. Lindberg·F. M. Marques·S. Masuoka·J. Mayer·K. Miki·T. Murakami·M. Najafi·K. Nakano·N. Nakatsuka·T. Nilsson·A. Obertelli·N. A. Orr·H. Otsu·T. Ozaki·V. Panin·S. Paschalis·D. M. Rossi·A. T. Saito·T. Saito·M. Sasano·H. Sato·Y. Satou·H. Scheit·F. Schindler·P. Schrock·M. Shikata·K. Shimada·Y. Shimizu·H. Simon·D. Sohler·L. Stuhl·S. Takeuchi·M. Tanaka·M. Thoennessen·H. Törnqvist·Y. Togano·T. Tomai·J. Tscheuschner·J. Tsubota·T. Uesaka·H. Wang·Z. Yang·M. Yasuda·K. Yoneda
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Abstract

The neutron-rich unbound fluorine isotope $^{30}$F$_{21}$ has been observed for the first time by measuring its neutron decay at the SAMURAI spectrometer (RIBF, RIKEN) in the quasi-free proton knockout reaction of $^{31}$Ne nuclei at 235 MeV/nucleon. The mass and thus one-neutron-separation energy of $^{30}$F has been determined to be $S_n = -472\pm 58 \mathrm{(stat.)} \pm 33 \mathrm{(sys.)}$ keV from the measurement of its invariant-mass spectrum. The absence of a sharp drop in $S_n$($^{30}$F) shows that the ``magic'' $N=20$ shell gap is not restored close to $^{28}$O, which is in agreement with our shell-model calculations that predict a near degeneracy between the neutron $d$ and $fp$ orbitals, with the $1p_{3/2}$ and $1p_{1/2}$ orbitals becoming more bound than the $0f_{7/2}$ one. This degeneracy and reordering of orbitals has two potential consequences: $^{28}$O behaves like a strongly superfluid nucleus with neutron pairs scattering across shells, and both $^{29,31}$F appear to be good two-neutron halo-nucleus candidates.

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J. Kahlbow, T. Aumann, O. Sorlin, Y. Kondo, T. Nakamura, F. Nowacki, A. Revel, N. L. Achouri, H. Al Falou, L. Atar, H. Baba, K. Boretzky, C. Caesar, D. Calvet, H. Chae, N. Chiga, A. Corsi, F. Delaunay, A. Delbart, Q. Deshayes, Z. Dombradi, C. A. Douma, Z. Elekes, I. Gasparic, J. -M. Gheller, J. Gibelin, A. Gillibert, M. N. Harakeh, A. Hirayama, M. Holl, A. Horvat, A. Horvath, J. W. Hwang, T. Isobe, N. Kalantar-Nayestanaki, S. Kawase, S. Kim, K. Kisamori, T. Kobayashi, D. Körper, S. Koyama, I. Kuti, V. Lapoux, S. Lindberg, F. M. Marques, S. Masuoka, J. Mayer, K. Miki, T. Murakami, M. Najafi, K. Nakano, N. Nakatsuka, T. Nilsson, A. Obertelli, N. A. Orr, H. Otsu, T. Ozaki, V. Panin, S. Paschalis, D. M. Rossi, A. T. Saito, T. Saito, M. Sasano, H. Sato, Y. Satou, H. Scheit, F. Schindler, P. Schrock, M. Shikata, K. Shimada, Y. Shimizu, H. Simon, D. Sohler, L. Stuhl, S. Takeuchi, M. Tanaka, M. Thoennessen, H. Törnqvist, Y. Togano, T. Tomai, J. Tscheuschner, J. Tsubota, T. Uesaka, H. Wang, Z. Yang, M. Yasuda, K. Yoneda. 2024-07-27. Magicity versus superfluidity around $^{28}$O viewed from the study of $^{30}$F. https://doi.org/10.1103/physrevlett.133.082501

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