Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 51 (2018)

Single-particle states and collective modes:
magnetic moment of 75m Cu
Y. Ichikawa,∗1 H. Nishibata,∗1,∗2 Y. Tsunoda,∗3 A. Takamine,∗1 K. Imamura,∗1,∗4 T. Fujita,∗1,∗2 T. Sato,∗1,∗5S. Momiyama,∗6 Y. Shimizu,∗1 D. S. Ahn,∗1 K. Asahi,∗1,∗5 H. Baba,∗1 D. L. Balabanski,∗1,∗7 F. Boulay,∗1,∗8,∗9J. M. Daugas,∗1,∗9 T. Egami,∗10 N. Fukuda,∗1 C. Funayama,∗5 T. Furukawa,∗11 G. Georgiev,∗12A. Gladkov,∗1,∗13 N. Inabe,∗1 Y. Ishibashi,∗1,∗14 T. Kawaguchi,∗10 T. Kawamura,∗2 Y. Kobayashi,∗1,∗15S. Kojima,∗5 A. Kusoglu,∗7,∗12,∗16 I. Mukul,∗17 M. Niikura,∗6 T. Nishizaka,∗10 A. Odahara,∗2 Y. Ohtomo,∗1,∗5T. Otsuka,∗1,∗3,∗6,∗18 D. Ralet,∗12 G. S. Simpson,∗19 T. Sumikama,∗1 H. Suzuki,∗1 H. Takeda,∗1 L. C. Tao,∗1,∗20Y. Togano,∗1,∗5 D. Tominaga,∗10 H. Ueno,∗1 H. Yamazaki,∗1 and X. F. Yang∗18
Atomic nuclei show dual features, the single-particle
shell nature and collective modes, which compete witheach other to express the actual nuclear structure. For
an attempt to describe the structural variety of unstable nuclei by using uniﬁed and general models, itis necessary to understand how the shell evolves in
unstable-nuclei regions, and how the shell competes
with the collectivity. In the present study, we demonstrate the precision analysis of this competition by focusing on the magnetic moment of an isomeric stateof a neutron-rich nucleus 75 Cu,1,2) where an intriguingshell evolution along the Cu isotopic chain has beenreported.3–5)
The experimental magnetic moment measurement
was conducted at the BigRIPS at RIBF, taking advantage of a spin-aligned RI beam obtained in a schemeof two-step projectile fragmentation with a techniqueof momentum-dispersion matching.6) The 75 Cu beamwith a spin alignment of 30(5)% was produced by one
proton removal from 76 Zn, which was a ﬁssion product of 238 U. The magnetic moment was determinedwith the time-diﬀerential perturbed angular distribution (TDPAD) method. Owing to the high spin alignment realized with the two-step scheme, the oscillationin the TDPAD spectrum was observed with a significance larger than 5σ. The magnetic moment of the66.2-keV isomer with spin parity 3/2− was determined
for the ﬁrst time to be µ = 1.40(6)µN .

Magnetic moment [ μN ]3.0μ(π p3/2)

2.0This workμ(π f5/2)

1.0

Exp. 3/2Exp. 5/2Calc. 3/2Calc. 5/2-preliminary0

Cu

69

Cu

71

73

Cu

Cu

7577

Cu

Cu

79

Fig. 1. Systematics of the magnetic moments for odd-A Cu
isotopes. Filled and open circles represent experimental
data for the 3/2− states and the 5/2− states, respectively. The filled red circle represents the result obtained in this work. The solid green and blue lines represent the MCSM calculations for the 3/2− states andthe 5/2− states, respectively, with the 20 ≤ (N, Z) ≤ 56
model space.7) µ(πp3/2 ) and µ(πf5/2 ) denote the proton Schmidt values for p3/2 and f5/2 , respectively.

The magnetic moment, thus obtained, shows a considerable deviation from the Schmidt value, µ =3.05µN , for the p3/2 orbital. Figure 1 shows the systematics of magnetic moments of the 3/2− and 5/2−states, where deviation from the Schmidt values appears to be maximal at 75 Cu. The analysis of the magnetic moment with the help of state-of-the-art shellmodel calculations7) reveals that the trend of the deviation corresponds to the eﬀect of the core excitation.
Furthermore, it was found that the low-lying states in75
Cu are, to a large extent, of single-particle nature on
top of a correlated 74 Ni core.

∗1RIKEN Nishina Center
Department of Physics, Osaka University∗3 Center for Nuclear Study, University of Tokyo∗4 Department of Physics, Meiji University∗5 Department of Physics, Tokyo Institute of Technology∗6 Department of Physics, University of Tokyo∗7 ELI-NP, IFIN-HH∗8 GANIL, CEA/DSM-CNRS/IN2P3∗9 CEA, DAM, DIF∗10 Department of Advanced Sciences, Hosei University∗11 Department of Physics, Tokyo Metropolitan University∗12 CSNSM, CNRS/IN2P3, Université Pris-Sud∗13 Department of Physics, Kyungpook National University∗14 Department of Physics, University of Tsukuba∗15 Department of Informatics and Engineering, University ofElectro-Communications∗16 Department of Physics, Istanbul University∗17 Department of Particle Physics, Weizmann Institute∗18 Intsituut voor Kern-en Srralingsfysica, K. U. Leuven∗19 LPSC, Université Grenoble Alpes, CNRS/IN2P3∗20 School of Physics, Peking University∗2References
1) J. M. Daugas et al., Phys. Rev. C 81, 034304 (2010).
2) C. Petrone et al., Phys. Rev. C 94, 024319 (2016).
3) T. Otsuka et al., Phys. Rev. Lett. 95, 232502 (2005).
4) S. Franchoo et al., Phys. Rev. Lett. 81, 3100 (1998).
5) K. T. Flanagan et al., Phys. Rev. Lett. 103, 142501(2009).
6) Y. Ichikawa et al., Nature Phys. 8, 918 (2012).
7) Y. Tsunoda et al., Phys. Rev. C 89, 031301(R) (2014).

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