Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 53

Study of 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,∗5A. Boso,∗5 S. Nishimura,∗6 V. H. Phong,∗6 J. Wu,∗6 P. -A. Söderström,∗6 T. Sumikama,∗6 H. Suzuki,∗6H. Takeda,∗6 D. S. Ahn,∗6 H. Baba,∗6 P. Doornebal,∗6 N. Fukuda,∗6 N. Inabe,∗6 T. Isobe,∗6 T. Kubo,∗6S. Kubono,∗6 H. Sakurai,∗6 Y. Shimizu,∗6 C. Sidong,∗6 B. Blank,∗7 P. Ascher,∗7 M. Gerbaux,∗7 T. Goigoux,∗7J. Giovinazzo,∗7 S. Grévy,∗7 T. Kurtukián Nieto,∗7 C. Magron,∗7 W. Gelletly,∗1,∗8 Zs. Dombrádi,∗7 Y. Fujita,∗9M. 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 the preliminary results of the analysis of the experiment NP1112-RIBF93
related to our study of the β-decay of 70 Kr. The main
goal of the experiment was to study p-n pairing andisospin-related eﬀects in the structure of 70, 71 Kr using
their β-decays as a probe.
70Kr nuclei were produced employing the fragmentation of a 78 Kr primary beam with an energy of345 MeV/nucleon and average beam currents around40 pnA. The primary beam impinged on a 5 mm thick
Be target to produce a cocktail radioactive beam. The
nuclear species of interest were then separated and selected using the BigRIPS separator. The nuclei werethen implanted in the WAS3ABi active stopper, surrounded by the EURICA γ-ray spectrometer1) for thestudy of their beta decay.
The level scheme of states in 70 Br populated in thebeta decay of 70 Kr has been deduced recently. Gammarays associated to the decay were identiﬁed using conventional β-γ and β-γ-γ coincidence techniques similarly to the procedure followed in Ref. 2). A primary
assignment of gamma rays was based on the determination of the half-lives obtained from implant-β-γ
correlations and their comparison with the half-life deduced from with implant-β correlations for the decay.
Then γ-γ coincidences and gamma intensities were employed to ﬁx their position in the decay level scheme.
Previous to our work, only the half-life of the decay

Fig. 1. Strongest identified gamma rays in the beta decayof 70 Kr. The spectrum is generated by requesting a
condition of gamma coincidences with beta transitions
correlated to 70 Kr implants in the analysis. Transitions
tagged with negative implant-β time correlations areshown in red.

was known with lower precision and no gamma rays
were associated to the decay.3) From the result of ouranalysis ﬁfteen gamma rays were identiﬁed for the ﬁrst
time and placed in the decay level scheme.4) In Fig. 1
we present the gamma spectrum generated in coincidence with beta transitions correlated to 70 Kr implants(in blue), that shows the most intense gamma rays.
Also for comparison, the gamma spectrum generated
in coincidence with background implant-beta correlations is given (in red). Presently, a comparison of theexperimental results with theoretical calculations5) is
performed in preparation for a publication.6)∗1IFIC, CSIC-Univ. Valencia
MTA ATOMKI∗3 ELTE-Budapest∗4 INFN-Legnaro∗5 INFN-Padova∗6 RIKEN Nishina Center∗7 CEN Bordeaux-Gradignan∗8 Department of Physics, Surrey University∗9 Osaka University∗10 CCHEN∗11 Institute of Nucl. Physics, Universität zu Köln∗12 Physik Department, Technische Universität München∗13 IFIN-HH, Bucarest∗14 Department of Physics, University of Istanbul∗15 Tokyo Univ. Sci.
∗16 IRFU, CEA, Universit Paris-Saclay∗17 GANIL-Caen∗18 Department of Physics, York University∗19 Department of Physics, University of Hong Kong
∗20 GSI, Germany∗2References

1) S. Nishimura, Prog. Theor. Exp. Phys. 2012, 03C006(2012).
2) A. I. Morales et al., Phys. Rev. C 95, 064327 (2017).
3) G. Gürdal, E. A. Mccutchan, Nuclear Data Sheets 136,1 (2016).
4) A. Vitéz-Sveiczer et al., Acta Phys. Polonica B 51, 587(2020).
5) P. Sarriguren, private communication.
6) A. Vitéz-Sveiczer et al., in preparation.

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