DOE OSTI · 2000354
Level structures of 56,58 Ca cast doubt on a doubly magic 60 Ca
Abstract
Gamma decays were observed in 56 Ca and 58 Ca following quasi-free one-proton knockout reactions from 57,59 Sc beams at ≈200 MeV/nucleon. For 56 Ca, a γ 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 $2^{+}_{1}\rightarrow0^{+}_{gs}$ 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 0$f$ 5/2 and 0$g$ 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.
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Chen, S., Browne, F., Doornenbal, P., Lee, J., Obertelli, A., Tsunoda, Y., Otsuka, T., Chazono, Y., Hagen, Gaute, Holt, J. D., Jansen, Gustav 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.. 2023-06-23. Level structures of 56,58 Ca cast doubt on a doubly magic 60 Ca. https://doi.org/10.1016/j.physletb.2023.138025
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