Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 51 (2018)

Spectroscopy of Sc isotopes between the N = 34 and N = 40 subshellclosures
P. Koseoglou,∗1,∗2 V. Werner,∗1 P.-A. Söderström,∗1,∗2 M. Lettmann,∗1 N. Pietralla,∗1 P. Doornenbal,∗3A. Obertelli,∗4,∗1,∗3 N. Achouri,∗4 H. Baba,∗3 F. Browne,∗3 D. Calvet,∗4 F. Château,∗4 S. Chen,∗5,∗6,∗3
N. Chiga,∗3 A. Corsi,∗4 M. L. Cortés,∗3 A. Delbart,∗4 J-M. Gheller,∗4 A. Giganon,∗4 A. Gillibert,∗4 C. Hilaire,∗4T. Isobe,∗3 T. Kobayashi,∗7 Y. Kubota,∗3,∗8 V. Lapoux,∗4 H. Liu,∗4,∗9 T. Motobayashi,∗3 I. Murray,∗3,∗10H. Otsu,∗3 V. Panin,∗3 N. Paul,∗4 W. Rodriguez,∗11,∗3 H. Sakurai,∗3,∗12 M. Sasano,∗3 D. Steppenbeck,∗3L. Stuhl,∗8 Y. L. Sun,∗4 Y. Togano,∗13,∗3 T. Uesaka,∗3 K. Wimmer,∗12,∗3 K. Yoneda,∗3 O. Aktas,∗9T. Aumann,∗1 L. X. Chung,∗14 F. Flavigny,∗10 S. Franchoo,∗10 I. Gasparic,∗3,∗15 R.-B. Gerst,∗16 J. Gibelin,∗17K. I. Hahn,∗18 D. Kim,∗19 T. Koiwai,∗12 Y. Kondo,∗20 J. Lee,∗6 C. Lehr,∗1 B. D. Linh,∗14 T. Lokotko,∗6M. MacCormick,∗10 K. Moschner,∗16 T. Nakamura,∗20 S. Y. Park,∗19 D. Rossi,∗1 E. Sahin,∗21 D. Sohler,∗22S. Takeuchi,∗20 H. Toernqvist,∗2 V. Vaquero,∗23 V. Wagner,∗1 S. Wang,∗24 X. Xu,∗6 H. Yamada,∗20 D. Yan,∗24
Z. Yang,∗3 M. Yasuda,∗20 and L. Zanetti∗1Z

Evidence for the existence of a new “magic number,”N = 34, has been obtained from the level structure of54
Ca1) while there may not be a corresponding shell
gap in Ti2,3) isotopes. This has created recent interest
to study the evolution of neutron-rich scandium isotopes. These nuclei lie between Ca and Ti and theevolution of proton orbitals can reveal the nature of
the magic numbers at N = 34, recently shown to vanish in 55 Sc,4) and the N = 40 pf -shell closure. In thiscase the valence proton occupies the πf7/2 orbital, interacting with νf5/2 orbital in 57, 59, 61 Sc.
The DALI2+ array has been coupled with the wide
acceptance SAMURAI spectrometer5) in the third
SEASTAR campaign. This made the measurement of
the energies of low-lying states of a large number ofisotopes in the previously discussed mass region possible. The radioactive beams were produced by a primary 70 Zn beam at 345 MeV/nucleon impinging on a10-mm-thick 9 Be target. The BigRIPS fragment separator6) was used for the identification and separation

26105

2524104

23103

2221102

20
19
18
2.55

102.6

2.65

2.7

2.75

2.8

2.85
A/Q

Fig. 1. Particle identification in BigRIPS after gating on
55–61
Sc in SAMURAI.

of the secondary beams. The Sc isotopes of interest
were produced by knock-out reactions in MINOS,7)
consisting of a 150-mm-thick LH2 target surroundedby an active TPC. Gamma rays were measured with
the DALI2+ array, consisting of 226 NaI(Tl) detectors surrounding MINOS. The reaction products wereidentfied event-by-event using two drift chambers anda hodoscope plastic-scintillator array after Brho analysis in the SAMURAI magnet. NEBULA and NeuLAND were used in addition for neutron detection.
Figure 1 shows all reaction channels producing 55–61 Sc.
In a preliminary analysis, the γ rays reported inRef. 4) for 55 Sc were identified in the data from theneutron knock-out reaction, 56 Sc (p,pn) 55 Sc. The fullanalysis of 55–61 Sc is on-going.

∗1Institut für Kernphysik, Technische Universität Darmstadt
GSI Helmoltzzentrum für Schwerionenforschung GmbH
∗3 RIKEN Nishina Center∗4 IRFU, CEA, Université Paris-Saclay∗5 School of Physics, Peking University∗6 Department of Physics, The University of Hong Kong
∗7 Department of Physics, Tohoku University∗8 Center for Nuclear Study, the University of Tokyo∗9 Department of Physics, Royal Institute of Technology∗10 Institut de Physique Nucléaire Orsay, IN2P3-CNRS∗11 Facultad de Ciencias, Departamento de Física, Sede Bogotá,Universidad Nacional de Colombia∗12 Department of Physics, University of Tokyo∗13 Department of Physics, Rikkyo University∗14 Institute for Nuclear Science & Technology, VINATOM∗15 Rudjer Boskovic Institute, Zagreb∗16 Institut für Kernphysik, Universität zu Köln
∗17 LPC Caen, ENSICAEN, Université de Caen
∗18 Department of Science Education, Ewha Womans University∗19 Department of Physics, Ewha Womans University∗19 Department of Physics, Tokyo Institute of Technology∗21 Department of Physics, University of Oslo
∗22 MTA Atomki∗23 Instituto de Estructura de la Materia, CSIC
∗24 Institute of Modern Physics, Chinese Academy of Sciences∗2References

1) D. Steppenbeck et al., Nature (London) 502, 207–210(2013).
2) D.-C. Dinca et al., Phys. Rev. C 71, 041302(R) (2005).
3) S. N. Liddick et al., Phys. Rev. Lett. 92, 072502 (2004).
4) D. Steppenbeck et al., Phys. Rev. C 96, 064310 (2017).
5) T. Kobayashi et al., Nucl. Instrum. Methods B 317,294–304 (2013).
6) T. Kubo et al., Prog. Theor. Exp. Phys. 2012, 03C003(2012).
7) A. Obertelli et al., Eur. Phys. J. A 50, 8 (2014).

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