Ⅱ-1. Nuclear Physics

RIKEN Accel. Prog. Rep. 51 (2018)

γ rays identified in the decay chain of 64 Se measured with EURICA

0

1000

2000

5360.8(11)5365.0(02)4238.12(59)3646.77(25)3651.02(36)3135.89(35)2565.77(08)3000

3366.94(12)2970.69(33)Ge Decay2764.83(55)0632485.45(39)500

1495.08(02)911.591(13)924.90(22) 953.94(11)1065.86(33)1331.79(07) 1349.87(28)1343.16(13) 1363.34(09)1494.71(12)1502.92(24)1691.56(14)1886.92(15)1937.13(24)1000

As Decay442.788(19) 482.247(93) 486.61(12)510.947(04)626.383(88) 640.84(17)636.74(13)647.07(14) 650.58(15)708.54(09)722.052(52)793.77(31)

2000
1500

72.516(62)75.059(23)367.336(90) 373.72(14)02500

1888.15(24)64

1888.34(04)2054.27(48)901.36(11)901.409(16)1259.20(24)1449.46(22)1494.53(19)510.764(59)Se Decay

1578.65(11)72.47(24)74.790(95)

500

64

1264.750(64)1300.53(06)1315.10(14) 1311.98(19)

2000
1500
1000

677.18(18)697.34(19)

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35
30
2520
1510
5
0

510.928(12)576.131(73)676.904(19)In a separate contribution to this Accel. Prog. Rep.1)
we have presented the preliminary results for the β delayed proton spectrum of 64 As decay and its T1/2 . This
was needed in order to fully understand the decay chain
following the decay of 64 Se (see Fig. 1 in the separatecontribution). Here we present some γ spectra thatwill help us to determine the complete decay chain.
All of the data for the two contributions come from anexperiment performed at RIKEN using the fragmentation of a 345 MeV/nucleon 78 Kr beam with typicalintensity of 200 pnA on a Be target. The fragments
were separated in flight using the BigRIPS separator
and implanted in three WAS3ABi double-sided Si stripdetectors. The implantation setup was surrounded by
the EUROBALL-RIKEN Cluster Array (EURICA).2)
It consisted of 12 Euroball IV type HPGe cluster detectors, each consisting of seven tapered, hexagonal HPGe
crystals at a nominal distance of 22 cm from the center.
We have analysed the γ spectra in prompt coincidencewith β signals happening in WAS3ABI in correlation
with the implantation signals happening in the same
pixel with the conditions set on 64 Se (T1/2 = 22.5 ms),
64As (T1/2 = 63.4 ms), and 63 Ge (T1/2 = 153.3 ms).
The corresponding γ spectra in “addback” mode (considering the full cluster as a single detector) are shownin Fig. 1. In green are the gamma lines which appear
in the spectrum with the condition on 64 Se implantation and not on the other two. Consequently they
are identified as γ rays associated with the beta decay of 64 Se. Similarly, the lines marked in pink appear
with the condition on 64 Se (as daughter activity) and64
As and disappear when the condition is set on 63 Ge,

72.48(43)75.50(18)417.507(87)Counts / 1 bin per keV

P. Aguilera,∗1,∗2 F. Molina,∗1 B. Rubio,∗2 J. Agramunt,∗2 A. Algora,∗2 V. Guadilla,∗2 A. Montaner-Piza,∗2
A. I. Morales,∗2 S. E. A. Orrigo,∗2 B. Blank,∗3 P. Ascher,∗3 M. Gerbaux,∗3 T. Goigoux,∗3 J. Giovinazzo,∗3S. Grévy,∗3 T. Kurtukian Nieto,∗3 C. Magron,∗3 D. Nishimura,∗4 J. Chiba,∗4 H. Oikawa,∗4 Y. Takei,∗4 S. Yagi,∗4D. S. Ahn,∗5 P. Doornenbal,∗5 N. Fukuda,∗5 N. Inabe,∗5 G. Kiss,∗5 T. Kubo,∗5 S. Kubono,∗5 S. Nishimura,∗5Y. Shimizu,∗5 C. Sidong,∗5 P. A. Söderström,∗5 T. Sumikama,∗5 H. Suzuki,∗5 H. Takeda,∗5 P. Vi,∗5 J. Wu,∗5Y. Fujita,∗6 M. Tanaka,∗6 W. Gelletly,∗2,∗7 F. Diel,∗8 D. Lubos,∗9 G. de Angelis,∗10 D. Napoli,∗10 C. Borcea,∗11A. Boso,∗12 R. B. Cakirli,∗13 E. Ganioglu,∗13 G. de France,∗14 and S. Go∗15

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5000

6000

Energy [keV]

Fig. 1. Spectra showing the γ rays measured with the Ge
array EURICA in correlation with implantation signal
happening in WASABI with conditions on 64 Se, 64 As,
and 63 Ge implanted ions (see text).

and are consequently associated with the β decay of64
As. Finally the γ rays associated with the decay of63
Ge are marked in red. Other possible activities inthe decay chain have longer half-lives. No β delayed γradiation was observed in any of the three cases prior
to this work. The corresponding level schemes are inpreparation.

∗1

Chilean Nuclear Energy Commision
IFIC, CSIC-Universidad de Valencia∗3 Centre d’Etudes Nucléaires de Bordeaux-Gradignan∗4 Department of Physics, Tokyo City University∗5 RIKEN Nishina Center∗6 Department of Physics, Osaka University∗7 Department of Physics, Surrey University∗8 Institute of Nuclear Physics, Universität zu Köln∗9 Physics Department E-12, Technische Universität München∗10 Istituto Nazionale di Fisica Nucleare, Laboratorio Nazionaledi Legnaro∗11 National Institute for Physics and Nuclear Engineering,
IFIN-HH∗12 Istituto Nazionale di Fisica Nucleare, Sezione di Padova∗13 Department of Physics, Istanbul University∗14 Grand Accélérateur National d’Ions Lourds∗15 Department of Physics, Tennessee UniversityReferences∗21) P. Aguilera et al., in this report.
2) P.-A. Söderström et al., Nucl. Instrum. Methods Phys.
Res. B 317, 649–652 (2013).

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