학술논문
Level Structures of $^{56,58}$Ca Cast Doubt on a doubly magic $^{60}$Ca
Document Type
Working Paper
Author
Chen, S.; Browne, F.; Doornenbal, P.; Lee, J.; Obertelli, A.; Tsunoda, Y.; Otsuka, T.; Chazono, Y.; Hagen, G.; Holt, J. D.; Jansen, G. R.; Ogata, K.; Shimizu, N.; Utsuno, Y.; Yoshida, K.; Achouri, N. L.; Baba, H.; Calvet, D.; Château, F.; Chiga, N.; Corsi, A.; Cortés, M. L.; Delbart, A.; Gheller, J. -M.; Giganon, A.; Gillibert, A.; Hilaire, C.; Isobe, T.; Kobayashi, T.; Kubota, Y.; Lapoux, V.; Liu, H. N.; Motobayashi, T.; Murray, I.; Otsu, H.; Panin, V.; Paul, N.; Rodriguez, W.; Sakurai, H.; Sasano, M.; Steppenbeck, D.; Stuhl, L.; Sun, Y. L.; Togano, Y.; Uesaka, T.; Wimmer, K.; Yoneda, K.; Aktas, O.; Aumann, T.; Chung, L. X.; Flavigny, F.; Franchoo, S.; Gasparic, I.; Gerst, R. -B.; Gibelin, J.; Hahn, K. I.; Kim, D.; Koiwai, T.; Kondo, Y.; Koseoglou, P.; Lehr, C.; Linh, B. D.; Lokotko, T.; MacCormick, M.; Moschner, K.; Nakamura, T.; Park, S. Y.; Rossi, D.; Sahin, E.; Söderström, P. -A.; Sohler, D.; Takeuchi, S.; Törnqvist, H.; Vaquero, V.; Wagner, V.; Wang, S.; Werner, V.; Xu, X.; Yamada, H.; Yan, D.; Yang, Z.; Yasuda, M.; Zanetti, L.
Source
Phys. Lett. B 843 (2023) 138025
Subject
Language
Abstract
Gamma decays were observed in $^{56}$Ca and $^{58}$Ca following quasi-free one-proton knockout reactions from $^{57,59}$Sc beams at $\approx 200$ MeV/nucleon. For $^{56}$Ca, a $\gamma$ ray transition was measured to be 1456(12) keV, while for $^{58}$Ca an indication for a transition was observed at 1115(34) keV. Both transitions were tentatively assigned as the $2^+_1 \rightarrow 0^+_{gs}$ decays, and were compared to results from ab initio and conventional shell-model approaches. A shell-model calculation in a wide model space with a marginally modified effective nucleon-nucleon interaction depicts excellent agreement with experiment for $2^+_1$ level energies, two-neutron separation energies, and reaction cross sections, corroborating the formation of a new nuclear shell above the $N$ = 34 shell. Its constituents, the $0f_{5/2}$ and $0g_{9/2}$ orbitals, are almost degenerate. This degeneracy precludes the possibility for a doubly magic $^{60}$Ca and potentially drives the dripline of Ca isotopes to $^{70}$Ca or even beyond.
Comment: 8 pages, 3 figures
Comment: 8 pages, 3 figures