1. Magicity versus superfluidity around $^{28}$O viewed from the study of $^{30}$F
- Author
-
Kahlbow, J., Aumann, T., Sorlin, O., Kondo, Y., Nakamura, T., Nowacki, F., Revel, A., Achouri, N. L., Falou, H. Al, Atar, L., Baba, H., Boretzky, K., Caesar, C., Calvet, D., Chae, H., Chiga, N., Corsi, A., Delaunay, F., Delbart, A., Deshayes, Q., Dombradi, Z., Douma, C. A., Elekes, Z., Gasparic, I., Gheller, J. -M., Gibelin, J., Gillibert, A., Harakeh, M. N., Hirayama, A., Holl, M., Horvat, A., Horvath, A., Hwang, J. W., Isobe, T., Kalantar-Nayestanaki, N., Kawase, S., Kim, S., Kisamori, K., Kobayashi, T., Körper, D., Koyama, S., Kuti, I., Lapoux, V., Lindberg, S., Marques, F. M., Masuoka, S., Mayer, J., Miki, K., Murakami, T., Najafi, M., Nakano, K., Nakatsuka, N., Nilsson, T., Obertelli, A., Orr, N. A., Otsu, H., Ozaki, T., Panin, V., Paschalis, S., Rossi, D. M., Saito, A. T., Saito, T., Sasano, M., Sato, H., Satou, Y., Scheit, H., Schindler, F., Schrock, P., Shikata, M., Shimada, K., Shimizu, Y., Simon, H., Sohler, D., Stuhl, L., Takeuchi, S., Tanaka, M., Thoennessen, M., Törnqvist, H., Togano, Y., Tomai, T., Tscheuschner, J., Tsubota, J., Uesaka, T., Wang, H., Yang, Z., Yasuda, M., and Yoneda, K.
- Subjects
Nuclear Experiment ,Nuclear Theory - 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., Comment: 9 pages, 2 figures, accepted for publication in Physical Review Letters
- Published
- 2024