Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 52 (2019)

Study of β-decay of 71 Kr
A. Sveiczer,∗1,∗2,∗3 A. Algora,∗1,∗2 A. I. Morales,∗1 B. Rubio,∗1 G. Kiss,∗2 J. Agramunt,∗1V. Guadilla,∗1 A. Montaner-Pizá,∗1 S. E. A. Orrigo,∗1 A. Horváth,∗3 G. de Angelis,∗4 D. Napoli,∗4 F. Recchia,∗5S. Lenzi,∗5 A. 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,∗7T. Goigoux,∗7 J. Giovinazzo,∗7 S. Grévy,∗7 T. Kurtukián Nieto,∗7 C. Magron,∗7 W. Gelletly,∗1,∗8 Zs. Dombrádi,∗7
Y. 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∗20In this paper, we present the preliminary results of theanalysis of the experiment NP1112-RIBF93, in particular, the ones related to our study of the β-decay of 71 Kr.
The main objective of the NP1112-RIBF93 experimentis to study p-n pairing and isospin-related features inthe structure of 70, 71 Kr through their β-decays.
71Kr nuclei were produced in the fragmentation of a78
Kr primary beam with an energy of 345 MeV/nucleon.
The high intensity beam provided by the accelerator
complex of the RI Beam Factory (RIBF) enabled us toachive primary beam currents around 40 pnA. The primary beam impinged on a 5 mm thick Be target to produce a cocktail beam. After the separation and selectionin the BigRIPS separator (see Fig. 1), the nuclei wereimplanted in the WAS3ABi active stopper, surroundedby the EURICA γ-ray spectrometer.1)
Standard β-γ and β-γ-γ coincidence techniques wereapplied to study the β-decay of 71 Kr. New γ transitions have been identiﬁed based on the comparisons between the half-lives obtained from implant-β-γ correlations and the half-life values determined from the corresponding correlations of previously identiﬁed γ-rays
that belong to the 71 Kr decay (198, 207 and 397-keVtransitions). In total, 4 new γ transitions have been
identiﬁed. After the identiﬁcation of all γ-rays that belong to this decay, γ-γ coincidences were also studied.
A new half-life value was determined using the implantβ-γ time correlations with coincidence conditions on thestrongest identiﬁed γ-rays of the decay. Several factors∗1IFIC, CSIC-Univ. Valencia∗2 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, Université Paris-Saclay∗17 GANIL-Caen∗18 Department of Physics, York University∗19 Department of Physics, University of Hong Kong
∗20 GSI

Fig. 1. Identification plot for the isotopes produced in 78 Kr
fragmentation for the 71 Kr setting.

Fig. 2. Half-life of 71 Kr determined in this work.

that can inﬂuence the quality of the ﬁt and the ﬁnal
value were taken into account as in our previous 70 Br
study.2) Figure 2 shows the half-life of the 71 Kr decay obtained with this method. The half-life obtained of T1/2
= 96.55(79) ms for this decay was signiﬁcantly consistent
with the previous measurements and it is the most precise value reported until now in the literature. Presently,
a new decay scheme is being constructed. The analysesof the 70, 71 Kr β and the possible 71 Kr isomer decays arestill in progress.
References

1) S. Nishimura, Prog. Theor. Exp. Phys. 03C006 (2012).
2) A. I. Morales et al., Phys. Rev. C 95, 064327 (2017).

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