Magic Nature of Neutrons in Ca-54: First Mass Measurements of Ca55-57

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

来源：Physical Review Letters, 2018, 121(2): 022506.

DOI：10.1103/PhysRevLett.121.022506

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 2p(1/2) and 1f(5/2) orbitals in Ca-54, comparable to the gap between the neutron 2p(3/2) and 2p(1/2) orbitals in Ca-52. For the Ca-56 nucleus, an open-shell property in neutrons is suggested.

• 出版日期2018-7-11
• 单位RIKEN