II-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

On the β-decay of 70 Kr
A. Vitéz-Sveiczer,∗1,∗2,∗3 A. Algora,∗1,∗2 A. I. Morales,∗1 B. Rubio,∗1 G. Kiss,∗2 J. Agramunt,∗1 V. Guadilla,∗1A. Montaner-Pizá,∗1 S. E. A. Orrigo,∗1 A. Horváth,∗3 G. de Angelis,∗4 D. Napoli,∗4 F. Recchia,∗5
S. Lenzi,∗5 A. Boso,∗5 S. Nishimura,∗6 V. H. Phong,∗6 J. Wu,∗6 P. -A. Söderström,∗6 T. Sumikama,∗6H. Suzuki,∗6 H. Takeda,∗6 D. S. Ahn,∗6 H. Baba,∗6 P. Doornebal,∗6 N. Fukuda,∗6 N. Inabe,∗6 T. Isobe,∗6T. Kubo,∗6 S. Kubono,∗6 H. Sakurai,∗6 Y. Shimizu,∗6 C. Sidong,∗6 B. Blank,∗7 P. Ascher,∗7 M. Gerbaux,∗7T. Goigoux,∗7 J. Giovinazzo,∗7 S. Grévy,∗7 T. Kurtukián Nieto,∗7 C. Magron,∗7 W. Gelletly,∗1,∗8 Zs. Dombrádi,∗7Y. Fujita,∗9 M. Tanaka,∗9 P. Aguilera,∗10 F. Molina,∗10 J. Eberth,∗11 F. Diel,∗11 D. Lubos,∗12 C. Borcea,∗13E. Ganioglu,∗14 D. Nishimura,∗15 H. Oikawa,∗15 Y. Takei,∗15 S. Yagi,∗15 W. Korten,∗16 G. de France,∗17P. Davies,∗18 J. Liu,∗19 J. Lee,∗19 T. Lokotko,∗19 I. Kojouharov,∗20 N. Kurz,∗20 and H. Shaﬀner∗20
In this contribution, we present preliminary resultsof the analysis of the β-decay of 70 Kr from the experiment NP1112-RIBF93. The main goal of the experiment was to study isospin-related eﬀects and p-n
pairing signatures in the region of A ∼ 70 using theinformation obtained from the β-decays of 70, 71 Kr.
To produce the isotopes of interest the fragmentation of a 78 Kr primary beam with an energy of
345 MeV/nucleon was used. Average beam currents of40 particle nA were provided by the RIKEN Nishina
Center accelerator complex. The 78 Kr primary beam
impinged on a 5 mm thick 9 Be target to produce
a cocktail radioactive beam. The fragments produced were then separated and selected using the BigRIPS separator. The ions were then implanted in theWAS3ABi active stopper, surrounded by the EURICA
γ-ray spectrometer1) for the study of their β decay.
Gamma rays associated to the de-excitation of states
populated in the daughter nucleus 70 Br were identiﬁed using conventional β-γ and β-γ-γ coincidence techniques similarly to the procedure followed in Ref. 2).
For more details see Refs. 3, 4). The analysis has also
allowed us to improve the precision of the deduced βdecay half-life and construct the level scheme of states
populated in the decay, which extends up to 3.3 MeV
excitation energy in 70 Br.
In Fig. 1 we present the deduced Gamow-Teller βFig. 1. Preliminary comparison of the experimental (black)and calculated accumulated B(GT) values for the 70 Kr→ 70 Br β decay.5) The experimental B(GT) uncertainties are determined by the feeding error of the levels
and the error of the half-life. The orange solid line
corresponds to the values calculated for the oblate minimum, the blue dashed line corresponds to the prolate
minimum of the ground state of 70 Kr.

strength in the daughter nucleus compared to the predictions of the pn quasiparticle random-phase approximation (pnQRPA) calculations for two possible deformation minima in 70 Kr.5) The calculations presented
here are based on the SLy4 force, which is a well tested
force throughout the whole nuclear chart. Alternative theoretical calculations are also performed usinga pseudo-LS model.6) We are presently working in theﬁnal details of a publication7) based on this study.

∗1IFIC, CSIC-Univ. Valencia
MTA ATOMKI∗3 ELTE TTK Fizikai Intézet∗4 INFN Laboratori Nazionali di Legnaro∗5 INFN Sezione di Padova∗6 RIKEN Nishina Center∗7 CEN Bordeaux-Gradignan∗8 Department of Physics, Surrey University∗9 Department of Physics, Osaka University∗10 Comisión Chilena de Energía Nuclear (CCHEN)∗11 Institut für Kernphysik, Universität zu Köln
∗12 Physik Department, Technische Universität München∗13 National Institute for Physics and Nuclear Engineering,
IFIN-HH∗14 Department of Physics, University of Istanbul∗15 Department of Physics, Tokyo University of Science∗16 IRFU, CEA, Université Paris-Saclay∗17 GANIL∗18 Department of Physics, York University∗19 Department of Physics, University of Hong Kong
∗20 GSI Helmholtzzentrum für Schwerionenforschung GmbH
∗2References

1) S. Nishimura, Prog. Theor. Exp. Phys. 2012, 03C006(2012).
2) A. I. Morales et al., Phys. Rev. C 95, 064327 (2017).
3) A. Vitéz-Sveiczer et al., RIKEN Accel. Prog. Rep. 53,28 (2019).
4) A. Vitéz-Sveiczer et al., Acta Phys. Pol. B 51, 587(2020).
5) P. Sarriguren, private communication.
6) P. Van Isacker, private communication.
7) A. Vitéz-Sveiczer et al., in preparation.

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