Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 47 (2014)

Decay spectroscopy around 78 N i with the EURICA setup
G. Benzoni,∗1 H. Watanabe,∗2,∗3 D. Sohler,∗4 E. Sahin,∗5 G. de Angelis,∗6 S. Nishimura,∗2 G. Lorusso,∗2T. Sumikama,∗7 P. Doornenbal,∗2 Z.Y. Xu,∗8 T. Isobe,∗2 P.A. Söderström,∗2 F. Browne,∗9 J. Wu,∗2,∗10H. Baba,∗2 Z. Patel,∗11 S. Rice,∗11 L. Sinclair,∗12 R. Yokoyama,∗13 R. Daido,∗14 Y. Fang,∗14 M. Niikura,∗8R. Avigo,∗1,∗15 F.L. Bello Garrote,∗5 N. Blasi,∗1 S. Ceruti,∗1,∗15 F.C.L. Crespi,∗1,∗15 M.-C. Delattre,∗16Zs. Dombradi,∗4 A. Gottardo,∗6 I. Kuti,∗4 K. Matsui,∗8 B. Melon,∗17 D. Mengoni,∗18 T. Miyazaki,∗8V. Modamio-Hoybjor,∗6 S. Momiyama,∗8 A.I. Morales,∗1,∗15 D. Napoli,∗6 R. Orlandi,∗19 H. Sakurai,∗2,∗8R. Taniuchi,∗8 J. Taprogge,∗20,∗21 Zs. Vajta,∗4 J.J. Valiente-Dobòn,∗6 O. Wieland,∗1 A. Yagi,∗14M. Yalcinkaya∗22
Exotic nuclei play an important role in nuclear shellstructure studies since they allow to search for possible modiﬁcations of magic numbers with increasing
N/Z ratio. The tensor force, one of the non-centralcomponents of the eﬀective nucleon-nucleon interaction, is expected to modify the relative single particle
energies owing to an increased attraction for orbitals
with anti-parallel spin conﬁguration and a repulsion
for orbitals with parallel spin conﬁguration. In suchcontest, nuclei at Z=28, N=50 shell gaps are particularly interesting since they are good candidates toreveal changes into the shell structure. Astrophysicalimplications also involve the discussion on neutron-richnuclei, since they are expected to dominate the nuclear
composition throughout the collapse of massive stars.
In this view an experiment aiming at studying decay spectroscopy in the region close to 78 Ni, i.e. in theisotopic chains of Cu, Ni, Co and Fe, was performed at
RIKEN in May 2013 as part of the EURICA campaign
at the Radioactive-Isotope Beam Factory (RIBF) facility.
The wanted species were produced by means of inﬂight ﬁssion of a 238 U beam at a bombarding energy of345 MeV/u. The resulting fragments were separatedin the BigRIPS separator, by the use of degraders at
the intermediate dispersive foci1) . The cocktail beam
was transported in the ZeroDegree spectrometer down

Fig. 1. PID plot of the cocktail beam implanted in theWAS3ABi array.

to the ﬁnal focal plane F11. The beam was thenslowed down in an Al degrader to ensure the implantation of the wanted species in the 5 silicon detectorsof the WAS3ABi array2) . This silicon array was surrounded by the EURICA spectrometer consisting of12 EUROBALL cluster detectors3) . LaBr3 scintillator
detectors were also mounted in clusters to allow fasttiming measurements. The experiment collected datafor an equivalent time of 3 days with an average primary beam intensity of 10pnA. The total count rate
at the ﬁnal focal plane F11 was limited to 100pps toensure ion-β correlations. In Figure 1 a particle identiﬁcation (PID) plot is shown. The plot does not include
the full statistics of the experiment. The Bρ setting of
the separator was set in order to transport 71 Fe in its
central trajectory.
The study of isomeric γ transitions and β-delayedtransitions in the populated nuclei is ongoing. Thesame reaction was also exploited to perform Coulomb
excitation reaction to study the ﬁrst excited states in73−75Ni isotopes4) .

∗1INFNRIKEN Nishina Center∗3 Beihang University∗4 MTA Atomki∗5 University of Oslo
∗6 LNL-INFN∗7 Tohoku University∗8 University of Tokyo∗9 University of Brighton∗10 Peking University∗11 University of Surrey∗12 York University∗13 CNS, University of Tokyo∗14 Osaka University∗15 Universitá degli Studi di Milano∗16 IPNO Orsay∗17 INFN sezione di Firenze∗18 Universitá degli Studi di Padova∗19 Instituut voor Kern- en StralingsFysica/K.U. Leuven∗20 Consejo Superior de Investigaciones Cientificas∗21 Universidad Autnoma de Madrid∗22 University of Instambul∗2References
1) T. Kubo: Nucl. Instr. Methods Phys. Res. Sect. B204,
97 (2003).
2) S. Nishimura: Prog. Theor. Exp. Phys. 2012, 03C006(2012).
3) P.-A. Söderström et al., Nucl. Instr. and Meth. B317,649 (2013).
4) A. Gottardo, this report.

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