Magic Nature of Neutrons in Ca 54: First Mass Measurements of Ca 55-57

S. Michimasa, M. Kobayashi, Y. Kiyokawa, S. Ota, D. S. Ahn, H. Baba, G. P.A. Berg, M. Dozono, N. Fukuda, T. Furuno, E. Ideguchi, N. Inabe, T. Kawabata, S. Kawase, K. Kisamori, K. Kobayashi, T. Kubo, Y. Kubota, C. S. Lee, M. MatsushitaH. Miya, A. Mizukami, H. Nagakura, D. Nishimura, H. Oikawa, H. Sakai, Y. Shimizu, A. Stolz, H. Suzuki, M. Takaki, H. Takeda, S. Takeuchi, H. Tokieda, T. Uesaka, K. Yako, Y. Yamaguchi, Y. Yanagisawa, R. Yokoyama, K. Yoshida, S. Shimoura

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Abstract

We perform the first direct mass measurements of neutron-rich calcium isotopes beyond neutron number 34 at the RIKEN Radioactive Isotope Beam Factory by using the time-of-flight magnetic-rigidity technique. The atomic mass excesses of Ca55-57 are determined for the first time to be -18650(160), -13510(250), and -7370(990) keV, respectively. We examine the emergence of neutron magicity at N=34 based on the new atomic masses. The new masses provide experimental evidence for the appearance of a sizable energy gap between the neutron 2p1/2 and 1f5/2 orbitals in Ca54, comparable to the gap between the neutron 2p3/2 and 2p1/2 orbitals in Ca52. For the Ca56 nucleus, an open-shell property in neutrons is suggested.

Original languageEnglish
Article number022506
JournalPhysical review letters
Volume121
Issue number2
DOIs
Publication statusPublished - Jul 11 2018

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All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

Michimasa, S., Kobayashi, M., Kiyokawa, Y., Ota, S., Ahn, D. S., Baba, H., ... Shimoura, S. (2018). Magic Nature of Neutrons in Ca 54: First Mass Measurements of Ca 55-57. Physical review letters, 121(2), [022506]. https://doi.org/10.1103/PhysRevLett.121.022506