Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 51 (2018)

Observation of new neutron-rich Mn, Fe, Co, Ni, and Cu isotopes
in the vicinity of 78 Ni†
T. Sumikama,∗1,∗2 S. Nishimura,∗2 H. Baba,∗2 F. Browne,∗3,∗2 P. Doornenbal,∗2 N. Fukuda,∗2 S. Franchoo,∗4G. Gey,∗5,∗2,∗6 N. Inabe,∗2 T. Isobe,∗2 P. R. John,∗7,∗8 H. S. Jung,∗9 D. Kameda,∗2 T. Kubo,∗2 Z. Li,∗10G. Lorusso,∗2 I. Matea,∗4 K. Matsui,∗11,∗2 P. Morfouace,∗4 D. Mengoni,∗12 D. R. Napoli,∗13 M. Niikura,∗11,∗2H. Nishibata,∗14,∗2 A. Odahara,∗14,∗2 E. Sahin,∗15 H. Sakurai,∗2,∗11 P.-A. Söderström,∗2 G. I. Stefan,∗4D. Suzuki,∗4,∗2 H. Suzuki,∗2 H. Takeda,∗2 R. Taniuchi,∗11,∗2 J. Taprogge,∗16,∗17,∗2 Zs. Vajta,∗18,∗2H. Watanabe,∗19,∗2 V. Werner,∗20 J. Wu,∗10,∗2 Z. Y. Xu,∗11,∗2 A. Yagi,∗14,∗2 and K. Yoshinaga∗21,∗2The neutron-rich nucleus 78 Ni is expected to be adoubly magic nucleus with the proton magic number
28 and the neutron magic number 50. To study themagicity of 78 Ni far from the stability line, the production of new isotopes beyond 78 Ni, such as the previous discovery of neutron-rich isotopes at RIBF,1) isthe first step.
In the present study, new isotopes in the vicinityof 78 Ni were produced via the in-flight fission reaction of a primary 238 U beam with a higher intensity than the previous one.1) The beam energy was
345 MeV/nucleon and the average intensity was 6.84
particle nA. The fission fragments were purified in theBigRIPS separator and transported to the ZeroDegree spectrometer. For particle identification, the timeof flight (TOF) and magnetic rigidities in the second
stage of BigRIPS, as well as the energy loss in a multisampling ionization chamber (MUSIC) placed at theend of the ZeroDegree spectrometer, were measured.
The atomic number, Z, and the mass-to-charge ratio,
A/Q, were deduced as shown in Fig. 1. A significancetest using p values was performed for 8 new isotopes
73
Mn, 76 Fe, 77,78 Co, 80,81,82 Ni, and 83 Cu, as described

3083Cu

2980

Ni

81Co

7828Z

77

2782

Ni

Ni

Co76Fe2673

Mn

25
24

2.8

2.85

2.9A/Q

2.95

Production Cross Section (ab)Fig. 1. Particle-identification plot of Z versus A/Q. Isotopes located on the right side beyond the red line werediscovered in the present study.

†Condensed from the article in Phys. Rev. C 95, 051601(R)(2017)∗1 Department of Physics, Tohoku University∗2 RIKEN Nishina Center∗3 School of Computing, Engineering and Mathematics, University of Brighton∗4 Institut de Physique Nucléaire (IPN), IN2P3-CNRS∗5 LPSC, CNRS/IN2P3, Institut National Polytechnique deGrenoble∗6 ILL∗7 Dipartimento di Fisica e Astronomia, Università di Padova∗8 Istituto Nazionale di Fisica Nucleare, Sezione di Padova∗9 Department of Physics, University of Notre Dame
∗10 Department of Physics, Peking University∗11 Department of Physics, University of Tokyo∗12 Dipartimento di Fisica, Universita di Padova∗13 Institute Nazionale di Fisica Nucleare, Laboratori Nazionali
di Legnaro∗14 Department of Physics, Osaka University∗15 Department of Physics, University of Oslo
∗16 Departamento de Fı́sica Teórica, Universidad Autónoma deMadrid∗17 Instituto de Estructura de la Materia, CSIC
∗18 MTA Atomki∗19 International Research Center for Nuclei and Particles in theCosmos, Beihang University∗20 Wright Nuclear Structure Laboratory, Yale University∗21 Department of Physics, Tokyo University of Science107

Cu

6Ni

10CoFe105Mn

10410378Co83Cu

10280Ni

1079Co73Mn

76Fe81Ni

110−182Ni

47

48495051525354Neutron NumberFig. 2. Production cross section as a function of the neutron number. The lines present model predictions.2)

in the previous study.1) The p values, which are allless than 1%, show evidence for these isotopes including the cases of 76 Fe, 81 Ni, and 82 Ni with a single event.
The production cross sections, shown in Fig. 2, werealso checked and found to be consistent with model
predictions.2)
References
1) T. Ohnishi et al., J. Phys. Soc. Jpn. 79, 073201 (2010).
2) O. B. Tarasov, D. Bazin, Nucl. Instrum. Methods B
266, 4657 (2008).

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