RIKEN Accel. Prog. Rep. 50 (2017)

Ⅰ. HIGHLIGHTS OF THE YEAR

Nuclear spectroscopy of multi-nucleon transfer reaction products in
the 136 Xe and 198 Pt system
Y. Hirayama,∗1 M. Mukai,∗2,∗3 Y.X. Watanabe,∗1 Y. Kakiguchi,∗1 P. Schury,∗1 M. Oyaizu,∗1 H. Miyatake,∗1M. Wada,∗1,∗2 M. Ahmed,∗1,∗3 S. Kimura,∗2,∗3 J.Y. Moon,∗4 J.H. Park,∗4 H. Ishiyama,∗4 S.C. Jeong,∗4S. Kanaya,∗5 H. Muhammad,∗5 A. Odahara,∗5 T. Shimoda,∗5 S. Suzuki,∗5 and H. Tsuru∗5radius for 199g Pt and 199m Pt from the spectrum analysis.

We have developed the KEK Isotope Separation
System (KISS)1) to study the β-decay properties ofneutron-rich isotopes with neutron numbers aroundN = 126 for astrophysics research2) . We extracted
elastic events of 198 Pt and unstable nuclei of 199,201 Pt
and 196,197,198 Ir produced in the 136 Xe beam and 198 Pt
target system3) . We successfully measured the lifetimeof these unstable nuclei, and measured the hyperﬁne
structure (HFS) of 199 Pt and 196,197 Ir in order to determine the magnetic dipole moment and the changein the charge radius by using the in-gas-cell laser ionization spectroscopy technique.
We performed nuclear spectroscopy using the 136 Xebeam with an energy of 10.75 MeV/nucleon and a maximum intensity of 100 pnA. We introduced a doughnutshaped gas cell with the 198 Pt rotating target system
in order to increase the extraction yield not only by increasing the 136 Xe primary beam intensity but also by
reducing the argon-gas plasma density in the gas cell.
The 136 Xe beam was directed onto the 198 Pt rotatingtarget placed in front of the gas cell, and was stopped
at a tungsten beam dump without entering the gascell. As a result, we successfully extracted the laser
ionized 199 Pt+ with a one order of magnitude higher
yield than that with a primary beam intensity of 20
pnA.
Figure 1 shows a typical β-decay curve of 197 Ir. The
half-life time was evaluated from the ﬁt to the spectrum where the decays of the parent nucleus 197 Ir
and daughter nucleus 197 Pt and a constant backgroundwere taken into account. The half-life times measured
in this experiment are listed in Table 1. The measured
half-life times t1/2 were in good agreement with thereported values.
Figure 2 shows the measured HFS of 199 Pt obtainedby detecting β-rays. We found that not only 199g Pt
but also 199m Pt were laser-ionized, from γ-ray measurement. This indicated that the measured HFS consists of the HFS of 199g Pt and 199m Pt. In order toidentify each HFS, we plan to measure the HFS bydetecting γ-rays emitted from 199m Pt, and then decompose the HFS of 199g Pt. It is feasible to evaluate
the magnetic dipole moment and the change in charge
∗1

∗2
∗3
∗4
∗5Fig. 1. Measured β-decay curve of 197 Ir. The red line indicates the best-ﬁt result to evaluate the half-life time.
Table 1. Comparison between the present measured andreported half-life times of 199,201 Pt and 196,197,198 Ir.

Extraction yield (arb. u.)

Nuclide
199
Pt
201
Pt
196
Ir
197
Ir
198
Ir

Measured t1/2
31.3(1.5) min
1.9(5) min
52(5) s6.1(4) min
10(1) sReported t1/2
30.8(2) min
2.5(1) min
52(1) s5.8(5) min
8(1) s2.5
2.01.51.00.50−40 −30 −20 −1001020 3040Frequency − 1204992.36 [GHz]Fig. 2. Measured hyperﬁne structure of 199 Pt.

References

Wako Nuclear Science Center (WNSC), Institute of Particle and Nuclear Studies (IPNS), High Energy Accelerator
Research Organization (KEK)
RIKEN Nishina Center
Department of Physics, University of Tsukuba
Institute for Basic Science, Rare Isotope Science Project
Department of Physics, Osaka University

1) Y. Hirayama et al., Nucl. Instr. Meth. B353, 4 (2015).
2) S.C. Jeong et al.: KEK Report 2010-2.
3) Y.X. Watanabe et al., Phys. Rev. Lett. 115, 172503(2015).

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