VIII-Ⅱ-1. Project Research
Project 3

PR3

Project Research on Science and Engineering of Unstable Nuclei and
Their Uses on Condensed Matter Physics

Y. Ohkubo
Research Reactor Institute, Kyoto University

Objective and Participating Research Subjects
The main objectives of this project research are theinvestigation of the nuclear structure of unstableneutron-rich nuclei and also the local properties ofmaterials using short-lived nuclei.
This period is the second year of the project.
The research subjects (PRS) executed in this period
are as follows:
PRS-1 Extension of usable fission products at KUR-ISOL
PRS-2 Determination of -ray intensities and evaluation of
-branching ratios for the decay of 147La to 147Ce.
PRS-3 Half-life measurements of excited levels in 149Pr.
PRS-4 (a) Dynamic perturbation to 111Cd(←111Ag) doped in AgI
nanoparticles; (b) Sites of impurities (140Ce) implanted in Fe.
PRS-5 (a) Dispersion state of Al and Cd impurities in ZnO; (b)Irradiation effect on the formation of defects in 57Co-doped
ZnO observed by the Mössbauer spectroscopy.
PRS-6 Mössbauer study of a parent material of Fe-based
superconductors, FeTe.
PRS-7 Study on rapid spin equilibrium and magnetic phasetransition for (C6H5)4P[MnIIFeIII(C2O3S)3] by means of highfield 57Fe Mössbauer spectroscopy.
PRS-8 Elucidation of a correlation between magnetic properties
and host-guest interactions in porous coordination polymers.
PRS-9 Characterization of gold clusters supported on zincoxide by 197Au Mössbauer spectroscopy.
PRS-10 129I Mössbauer spectroscopy of AgI nanoparticles.

Main Results and Contents of This Report
In order to extend usable radioactive ion beams at
KUR-ISOL, A. Taniguchi et al. (PRS-1) searched forneutron-rich Sr and Y isotopes and have observed 99Sr
with a half-life t1/2 of 269 ms (the shortest among thenuclides extracted at KUR-ISOL) and 101Y.
For 147La(→147Ce) obtained at KUR-ISOL, Y. Shimaet al. (PRS-2) determined the values of 244 relative Is
and 82 Is, using a coaxial 60% HPGe detector. They
reevaluated the value of I for 147La→147gCe to be 18%.
For 149Ce(→149Pr) obtained at KUR-ISOL, Y. Kojima
et al. (PRS-3) measured the t1/2s of the 58.2-keV and
125.6 keV levels in 149Pr, using a radiation detection
system consisting of a high-purity Ge detector, a thinplastic scintillator and a LaBr3 one.
Using the excited level with a nuclear spin I = 5/2 andt1/2 = 85 ns of 111Cd(←111Ag), W. Sato et al. (PRS-4a)observed a dynamic perturbation pattern in the TDPAC
spectrum for AgI nanoparticles coated with a polymer(PVP) at room temperature, implying a hopping motionof Ag in AgI, while no perturbation was observed atroom temperature for AgI with no polymer. Using theexcited level with I = 4 and t1/2 = 3.5 ns of 140Ce(←140La←140Ba←140Cs), Y. Ohkubo et al. (PRS-4b) obtained the
TDPAC result that about 30% of 140Ce implanted in Fe
occupy the substitutional Fe sites with no lattice defects
nearby and feel the unique static magnetic hyperfine
field.
Using the excited level of 111Cd(←111mCd), S.
Komatsuda et al. (PRS-5a) obtained the TDPAC resultthat Cd ions doped in ZnO disperse and reside solely at
the substitutional Zn sites, while Al ions disperse in ZnO
in the form of considerably large aggregates of their own.
W. Sato et al. (PRS-5b) incorporated defects in 57Codoped ZnO by electron beam irradiation at KURRILINAC and found no indication of magnetism whichmight be induced in ZnO in the 57Fe Mössbauer
spectrum for the irradiated ZnO.
S. Kitao et al. (PRS-6) took 57Fe Mössbauer spectra
for FeTe0.9 in a temperature range between 5 K and 290
K and obtained the result indicating the existence of astructural phase transition accompanied by a magnetictransition.
N. Kojima et al. (PRS-7) obtained the temperatureand magnetic field dependences of 57Fe Mössbauer
spectra for (C6H5)4P[MnIIFeIII(C2O3S)3] (1-mto). Theyobtained the following results: Although 1-mto
undergoes magnetic phase transitions at 30 K and 23 K,
the spin state of Fe(III) is paramagnetic above 23K, there
being rapid equilibrium between the high and low spinstates. Below 23 K, the spins of Fe(III) are ordered. The
critical external magnetic field for the Fe(III) spin-floptransition is higher than 8 T.
M. Ohba et al. (PRS-6) synthesized Fe(II) porous
coordination polymers (PCPs). Employing 57Fe
Mössbauer spectroscopy on the PCPs, they obtained theresult among others that depending on the guest
molecule, PCPs exhibit different magnetic behavior.
Applying XAS and 197Au-Mössbauer spectroscopy toa study on gold nanoparticles supported on ZnO (H2), H.
Ohashi et al. (PRS-9) obtained the results that Zn is not
reduced and that some Au exist as Au(0), forming
relatively uniform clusters.
Yamamoto et al. (PRS-10) applied 129I-Mössbauer
spectroscopy at 13 K to obtain information of thechemical state of Ag in AgI nanoparticles coated with
PVP. From the observation of the valence of iodine
being different from -1, they considered that this valencechange is due to an interaction between the surface of thenanoparticles and PVP, which may stabilize the hightemperature phase involving in superionic conductivity.

採択課題番号 24P3
不安定原子核の理工学と物性応用研究（京大・原子炉）大久保嘉高

プロジェクトPR3-1

Extension of Usable Fission Products at KUR-ISOL

Fission yield (Cumrative)

97

10

10

0

102
99

Sr

Sr

Y
101

128

Y

In

127

In

−
126

10

6

Counts
Nd 319.4

10

4

147

Nd 275.4
147

Sr 125.1

Nb 137.7

899

Y 121.7

Nb 97.8

99

99

99

Nd 120.5

2

147

10

10

(a) B.G. Spectrum
0

100
200
−ray energy (keV)

300

In

−
1

4

(b) A=99 Spectrum

Fig.2 (a) Background -ray spectrum before the ion-beam ison. Mainly observed-rays are from 147Nd (T1/2=10.98 d)
because an A=147 beam was used in other experiment before
this experiment and the inside of the collection chamber wascontaminated. (b) The -ray spectrum for A = 99. Representative -rays emitted in the decay of 99Sr were observed.
(The accumulation time of this spectrum was 1000 s.)

Sr
98

10

10

Nd 91.8

INTRODUCTION: At ISOL facilities in the world, avariety of radioisotope ion beams are produced using
various nuclear reactions. The variety of usable RI beams
is one of important characteristics of RI beam facilities.
Here at KUR-ISOL (Kyoto University Reactor-Isotope
Separator On-Line), we have been trying to extend usable
RI beams. In a previous period, we successfully obtained
beams of 97Sr and 98Sr, which have rather short life for
ISOL coupled to a gas-jet system like ours [1]. Moreover,although indium isotopes had never been attempted to
extract at KUR-ISOL and therefore their availability had
not been known, extraction of 126-128In beams were also
performed by careful tuning of an ion source and a
mass-analyzing electromagnet [2]. In Fig.1 are plottedvalues of yield vs. half-life for thermal fission products of235
U including a part of usable nuclei at KUR-ISOL. In
this period, 99Sr (T1/2=269 ms) and 101,102Y (T1/2=448 ms
and T1/2=300 ms) were chosen as next candidates, andextraction of 99Sr and 101, 102Y was attempted.
EXPERIMENTS: The 235UF4 target of 50 mg was irradiated at KUR-ISOL under 1 or 5 MW reactor operation.
The fission products were transported using the He/N2
gas-jet system to a surface-ionization type ion-source. Srand Y were ionized and extracted in the form of Sr+ and
YO+, and then mass-separated using an electromagnet
and collected on an aluminized Mylar tape. The yields
were measured by detecting representative -rays with a
30% Ge detector placed at an in-beam position. The op-

147

Research Reactor Institute, Kyoto University
1
Radioisotope Research Center, Nagoya University

timal values of the magnetic field and the input power ofthe ion source were determined on the basis of the previous KUR-ISOL operation.
RESULTS and CONCLUSION: Fig. 2 shows the -ray
energy spectra for the mass number A = 99 and for the
background during the experiment. Representative -rays
from 99Sr and its descendant nuclides were observed. 99Sr
has become a nuclide having the shortest half-life among
those observed at KUR-ISOL. Moreover, although amore detail analysis is required, -rays from 101Y and its
descent nuclides seem to have been observed in the
A=101 energy spectrum. But, as for the A=102 spectrum,
-rays from 102Y were not clearly seen while -rays from102
Nb were easily identified. This observation might beunderstood by invoking the facts that both the fission
yield and the hale-life of 102Nb are much larger than thoseof 102Y. However, it is known that ionization of NbO isdifficult in the case of using a surface ionization ion
source. We therefore need to examine the observation
carefully.

CountsA. Taniguchi, Y. Ohkubo, M. Tanigaki, M. Shibata1 and Y.
Kojima1

0

10
10
Half life of fission product (sec)101

Fig.1 Yield vs. half-life for a part of the 235U thermal fission products [3]. The filled circles represent the usable
nuclei at KUR-ISOL and the open circles are for nuclei
which have not yet extracted.

REFERENCES:[1] A. Taniguchi et al., KURRI Prog. Rep. 2010 (2011)90.
[2] A. Taniguchi et al., KURRI Prog. Rep. 2011 (2012)172.
[3] T. R. England and B. F. Rider, LA-UR-94-3106,
ENDF-349.

採択課題番号 24P3-1 オンライン同位体分離装置における生成核種の拡張とプロジェクト精密制御に関する研究（京大・原子炉）谷口秋洋、大久保嘉高、谷垣 実（名大・RI センター）柴田理尋、小島康明

Determination of -Ray Intensities and Evaluation of -Branching Ratios
for the Decay of 147La to 147Ce

採択課題番号 24P3-2

102

present results
ENSDF

10

1

10

0

3045

2500

2156

1903

1712

1298

1148

924.3

-1

10

673.1

INTRODUCTION:
Decay schemes are essential
information as nuclear data. In particular, those of fission
products are important for studies of nuclear physics andengineering. For example, - and -ray energies, -rayintensities I and-branching ratios Iare necessary for
decay heat calculations.
Until now, high energy excited levels and -raytransitions in 147Ce and 145La have been identified
through the decay spectroscopy on 147La and 145Ba with a4 clover detector [1]. In order to deduce these I values,
coincidence summing corrections based on the proposed
decay schemes are necessary because of the large solid
angle of the clover detector. In this study, to verify thecorrection, we measured -rays from the decay of 147La ina far geometry and deduced the reliable I as a reference.
In addition, the Ivalues for 147La→ 147Ce were also
evaluated.
EXPERIMENTS: The intensities of -rays from 147La
were measured with a coaxial 60% HPGe detector. The
detector was placed at 20 cm from a 147La source. A
10-mm-thick plastic -absorber was installed in front of
the detector end cap. The detector was shielded with
5-mm-thick copper plates, 10-cm-thick lead blocks andboron-doped 5-cm-thick polyethylene blocks.
147
La isotopes were produced with neutron-induced
fission of 235U and mass-separated with KUR-ISOL. The
mass-separated isotopes were collected on an aluminized
Mylar tape and periodically transported to a measurement
position. The tape cycle was set to be 8.0 s. Gamma-rays
from 147La were measured for 46 h.
The efficiency curve for the HPGe detector wasdetermined using 152Eu and 133Ba. The efficiencies werealso calculated with the Monte-Carlo simulation code
GEANT4. The accuracy of the peak efficiencies wasevaluated to be 1% from the difference between theexperimental values and the calculated ones.
Using peak counts obtained from the singles spectrum
and the peak efficiencies, Is for 147La → 147Ce werededuced. The Is were calculated from the -ray intensity
imbalance taking account of previously reported internalconversion coefficients.
RESULTS: In this experiment, 244 relative Is were438.2

Graduate School of Engineering, Nagoya University
1
Institute of Health Biosciences, The University of Tokushima Graduate School2
Radioisotope Research Center, Nagoya University
3
Research Reactor Institute, Kyoto University

determined for the decay of 147La; 59 intensities wererevised and 185 intensities were deduced for the first time.
Fig. 1 shows the Is for 147La→ 147Ce. The open andclosed bars represent previously reported values [2] andour present results, respectively. In this analysis, Is for
82 energy levels from 0 to 3045 keV were obtained. As
shown in Table 1, the I for the decay to 147gCe decreases
from 29% to 18% because Is for high energy levels were
newly identified. Consequently, the log-ft value was
evaluated to be 5.9.
CONCLUSIONS: We determined 244 relative Is forthe decay of 147La and Is for 82 levels in 147Ce. The I forthe ground state was reevaluated to be 18%.
Measurements of high energy levels are necessary to
determine accurately the I value for 147La → 147gCe.
Compared to the present data, the data obtained with theclover detector have one order of magnitude better
statistics. Demonstration of validity of the coincidence
summing correction is now in progress.

0
215.4

Y. Shima, H. Hayashi 1 , Y. Kojima 2 , A. Taniguchi 3 and
M. Shibata 2



PR3-2

Level energy (keV)
Fig.1. -branching ratio Ifor 147La→147Ce. The values
for the levels higher than 924.3 keV have been obtained
for the first time.

Table 1. -branching ratio I and log-ft value for 147La→
147g
Ce.
present results
ENSDF
18
29
I(%)
log-ft5.9
5.63
REFERENCES:[1] Y. Shima et al., Proc. Int. Conf. on Nuclear Data for
Science and Technology 2013 (submitted).
[2] Evaluated Nuclear Structure Data File (ENSDF),
http://nndc.bnl.gov/ensdf.

全吸収検出器を用いた核分裂生成物の高励起準位のプロジェクト
解明に向けた崩壊核分光研究（名大・RIC）柴田理尋、小島康明（名大院・工）嶋 洋佑（徳島大・医）林 裕晃（京大・原子炉）谷口秋洋

Half-Life Measurements of Excited Levels in 149Pr

Y. Kojima, Y. Shima1, H. Hayashi2, A. Taniguchi3 and
M. Shibata
Radioisotope Research Center, Nagoya University
1
Graduate School of Engineering, Nagoya University
2
Institute of Health Biosciences, The University of Tokushima Graduate School3
Research Reactor Institute, Kyoto University

INTRODUCTION: Half-lives of nuclear excited levels
are one of the most important nuclear data. For example,
precise determination of the half-life is necessary for nuclear applications such as material science because it relates to the natural width of the level. Knowledge of thehalf-lives also makes it possible to determine the -ray
reduced transition probabilities or nuclear matrix elements, which are useful for studying nuclear structure.
Although half-life data provide valuable information to
nuclear science, half-lives of only a limited number oflevels in fission products have been measured because
these nuclides are difficult to produce and most of thelevels are short-lived.
To measure nuclear level half-lives down to
sub-nanosecond, we have installed a spectrometer at theon-line isotope separator KUR-ISOL. To date, thehalf-lives of 148Ce, 148Pr and 149Nd have been successfullymeasured using this apparatus [1,2]. In this report, we
present our recent experimental results on 149Pr.
EXPERIMENTS: The parent nuclide of 149Pr, i.e. 149Ce
was prepared at KUR-ISOL, following the thermal neutron-induced fission of 235U. The fission products were
thermalized in the target chamber, and transported to athermal ion source by gas jet stream. After ionization, thenuclides were extracted, accelerated to 30 keV, andmass-separated with a resolution of M/M~600. The
mass-separated beams were implanted into an aluminum-coated Mylar tape, and periodically moved to thelead-shielded detector station.
At the detection port, we placed a LaBr3 scintillator (1.5
× 1.5 inch), a 1-mm-thick plastic scintillator and ashort-coaxial Ge detector. The level half-lives were
measured by means of the  delayed coincidence
technique. In this method, the time difference between and  detection was measured using a time-to-amplitude
converter (TAC); The  signal from the plastic scintillator
started the TAC unit, and the  signal from the LaBr3
stopped it. The Ge detector was used for selecting a desired  transition branch through off-line sorting. The
 coincidence data were recorded in list mode.
RESULTS: Fig. 1 shows two notable decay curves obtained for 149Pr. Note that we analyzed the data based on
the decay scheme reported in Refs. [3,4]. A slope isclearly observed in each figure. The half-life was de-

採択課題番号 24P3-3

duced through the least-squares fitting method using a
exponential function. The results are summarized in Table 1.
The half-life of 7.2(6) ns which we obtained for the
58.2-keV level is approximately consistent with thehalf-life of 10(2) ns reported in Ref. [4]. Our data hasmuch improved the precision and reliability. This is because the time resolution of our spectrometer is superior
to that in the previous work, in which a planar Ge detector was used as a timing  detector. We also report thefirst measurements of the half-lives for the 86.5- and125.6-keV levels, although the relative uncertainties arelarge due to low statistics.
SUMMARY: We measured level half-lives for 149Pr including two first experimental results. These data should
be indispensable in discussing the nuclear structure.
10

2
149

(a)

Ce

10

2
149

(b)

Ce

163.1

448.3

105 (HPGe)

323 (HPGe)

58.2

125.6

58 (LaBr 3)Counts / channel

PR3-3

149

Pr

67 (LaBr 3)

0

149

10

10

Pr

58.2

1

1

T1/2 =
7.2(8) ns

T1/2 =
1.02(20) ns
0

160

170

(1.22 ns/ch)10
180 310Channel number

320

330

(610 ps/ch)

Fig. 1. Decay curves observed for (a) the 58.2-keV and(b) the 125.6-keV levels in 149Pr. The energy gates used
to obtain these decay curves are shown in the insets.
The closed circles represent the fitting region.
Table 1. Half-lives obtained for the excited levels in 149Pr .
Level
(keV)
58.2
58.2
86.5
86.5
125.6

Gate (keV)
LaBr3 HPGe
58.2
104.9
58.2
172.6
86.5
76.5
86.5
129.1
67.4
322.5

Slope
7.2(8)
7.1(10)4.0(8)
4.3(7)
1.0(2)

Half-life (ns)Ave.
Ref.[4]7.2(6)

10(2)

4.2(5)－

1.0(2)－REFERENCES:[1] Y. Kojima et al., Nucl. Instr. Meth., A 659 (2011)
193-197.
[2] Y. Kojima et al., Proc. Int. Conf. on Nuclear Data for
Science and Technology 2013 (submitted).
[3] B. Singh, Nucl. Data Sheets 102 (2004)1-292.
[4] K. Yamauchi et al., KURRI-KR-3, pp.51-53, (in Japanese).

核分裂生成物に対する励起準位寿命測定を
プロジェクト中心とした崩壊核分光（名大・RIC）小島康明、柴田理尋 （名大院・工）嶋 洋佑 （徳島大・医）林 裕晃（京大・原子炉）谷口秋洋

PR3-4

Dynamic Perturbation to 111Cd(←111Ag) Doped in AgI Nanoparticles

W. Sato, R. Mizuuchi1, S. Komatsuda1, S. Kawata2, A.
Taoka and Y. Ohkubo3
Institute of Science and Engineering, Kanazawa
University
1
Graduate School of Natural Science and Technology,
Kanazawa University
2
Department of Chemistry, Faculty of Science, Fukuoka
University
3
Research Reactor Institute, Kyoto University

INTRODUCTION: It is well known that silver iodide(AgI) offers superionic conductivity as in its
high-temperature  phase, and applications of thissolid-state conductivity are desired in a wide field ofindustry.
This conducting phenomenon, however,
emerges at high temperature because of temperaturedependent crystal structures, which is indeed a barrier topractical applications of this compound.
Recently, an epoch-making technique was reported
to break through this situation: AgI powder coated with
poly-N-vinyl-2-pyrrolidone (PVP) can drasticallyenhance the ionic transport property at room temperature,
recording the conductivity of 1.5 × 10-2 -1 cm-1 [1].
The authors of Ref. [1] report that this achievement is due
to successful control of the particle size as small as
nanoscale.
For a detailed understanding of ionic
conductivity of this binary solid, it is of great importance
to examine lattice-to-lattice hopping motion of Ag+ ionson an atomic scale. For that purpose, in the present
work, dynamic behavior of Ag+ ions has been observedby means of the time-differential perturbed angularcorrelation (TDPAC) technique using the probe of111
Cd( ← 111Ag) nuclei. Here, preliminary results ofsuccessful observation of room-temperature dynamic
motion of Ag+ ions are reported.
EXPERIMENTS: For the production of the TDPAC
probe, Pd foil was irradiated with thermal neutrons in
Kyoto University Reactor. After radioequilibrium wasachieved between 111Pd and 111Ag, the Pd foil was
dissolved in HNO3 aq. solution, and carrier-free 111Ag
was isolated by an anion exchange chromatography.
The separated 111Ag was incorporated in AgI samples
when the powder sample was synthesized by
precipitation. In the present work, two different AgI
samples were prepared: PVP-free and PVP-coated. We
confirmed by transmission electron microscopy thatmicroscopic particles with sizes of 10-100 nm weresynthesized for 111Ag-free PVP-coated AgI.
TDPAC measurements of the 111Cd(←111Ag) probe
were performed for both samples at various temperatures

to observe temperature dependence of the spectra. The
directional anisotropy, A22G22(t), was deduced from thefollowing relation:
A22G22 (t ) 

2[ N ( , t )  N ( / 2, t )].
N ( , t )  2 N ( / 2, t )(1)Here, A22 denotes the angular correlation coefficient,
G22(t) the time-differential perturbation factor as afunction of the time interval, t, between the relevant
cascade -ray emissions, and N(, t) the number of thedelayed coincidence events observed at an angle, .
RESULTS: For the PVP-free AgI polycrystals, no time
variation is seen in the TDPAC spectrum at room
temperature, which suggests that the 111Cd( ← 111Ag)
probe duly occupies the tetrahedral lattice sites of Ag+ inzinc blende crystal structure as in the  phase. In thehigh-temperature (> 419 K)  phase, the TDPAC spectra
show an exponential relaxation, signifying a dynamic
perturbation on the probe nucleus.
As regards the PVP-coated AgI nanoparticles, on
the other hand, typical dynamic perturbation wasobserved even at room temperature as shown in Fig. 1.
The directional anisotropy of the spectrum shows arelaxation in the time scale of 10-7 s, which corresponds
to nuclear relaxation time by the dynamic perturbation
arising from fast fluctuation of the extranuclear charge
distribution, namely, hopping motion of Ag + ions. It isconsidered that PVP-coating has made it possible for the phase to survive at room temperature, realizing
superionic conductivity.
For evaluating the hopping rate of Ag+ ions, it isessential to obtain the value of nuclear quadrupole
frequency as they are still at their lattice site.
Experiments for the data acquisition are now in progress.

Fig. 1. TDPAC spectrum of 111Cd(←111Ag) in PVP-coated
AgI at room temperature.

REFERENCE:[1] R. Makiura et al. Nature Mater. 8, (2009) 476 – 480.

採択課題番号 24P3-4a 超イオン伝導体 AgI 中の放射性核での電気四重極相互作用 プロジェクト（京大・原子炉）大久保嘉高、谷口秋洋、谷垣 実（金沢大・理工研究域）佐藤 渉（金沢大院・
自然）水内理映子

Sites of Impurities (140Ce) Implanted in Fe

Y. Ohkubo, A. Taniguchi, Q. Xu, and M. Tanigaki
Research Reactor Institute, Kyoto University

INTRODUCTION: Cerium does not form a solid
solution with iron. It is interesting to examine where Ceions occupy in Fe when they are implanted in it. If Ceions reside in the substitutional sites, the nuclei of Ceshould feel a large hyperfine magnetic field, Bhf. Thistime, we applied the time-differential perturbed angularcorrelation (TDPAC) technique to the 2083 keV state of140
Ce implanted in Fe, and observed that about 35% of Ce
felt a large hyperfine magnetic field, which in turn
indicates that this amount of Ce ions are located at thesubstitutional sites. Incidentally, from the Larmor
frequency, L, measured with the TDPAC method and areported value of the Bhf at 141Ce in Fe, -41(2) T, we could
derive the magnetic moment, , of the 2083 keV state of140
Ce (see Ref. [1] about the obtained  value and acomparison of it with two shell-model calculation results).
EXPERIMENTS: Room-temperature implantation of
100-keV 140Cs ions was performed on an Fe foil at
KUR-ISOL, and in a different run a similar implantation
was done in order to check reproducibility. Each of the two
Fe foils was 0.1-mm thick and of 99.995% purity, which
had been annealed in H2 atmosphere at 700°C for 2 h andpolished. 140Cs decays to 140Ce through 140Ba and then 140La.
We name these samples 140CeFe.
The time dependences of the coincidence counts N(, t)of the 329-487 keV cascade  rays accompanying the beta
decay of 140La in the two Fe samples were taken at room
temperature with two measurement systems, eachconsisting of standard fast-slow electronic modules andfour BaF2 scintillation detectors. Here,  and t denote theangle and the time interval, respectively, between the
cascade  rays. The directional anisotropy A22G22(t) is
obtained as follows:

A22G 22 (t )  2

N (180, t )  N (90, t ).
N (180, t )  2 N (90, t )with Bext was reversed with the inversion of the external
magnetic field. The amplitude of the oscillation, i.e., theeffective A22 value (and the L value) for the 1st sample are-0.042 (and +1927(7) Mrad/s) and those for the 2nd sample-0.051 (and +1930(8) Mrad/s). These amplitudes are muchsmaller than a reported A22 value of -0.13, indicating that
only 30-40% of the 140Ce implanted in Fe feel the uniquestatic magnetic hyperfine interaction. This value is close to
the fraction of Ce that was considered to occupy thesubstitutional Fe sites, 28.9(5)%, obtained in a nuclear
orientation (NO) measurement on 141Ce in Fe [2], although141
Ce ions were directly implanted into an Fe foil, while inour case 140Cs ions, 140Ce’s precursors, were implanted. In
NO, the so-called two-site model is used, in which afraction of impurity nuclei occupy “good sites”,
experiencing the full hyperfine interaction and theremainder zero interaction. Our A22 value may justify theuse of the two-site model for 141CeFe and implies that asame fraction of Cs, Ba and La also occupy “good sites” in
Fe.
-0.10

0.00

-0.10

RESULTS: In Fig. 1 are shown the two TDPAC spectra
obtained for the two 140CeFe samples. A clear oscillation
pattern can be seen in both spectra, and the frequencies
and amplitudes are identical with each other. As for theoscillation pattern, reproducibility has therefore been
confirmed. From another TDPAC measurement on the 1st
sample using three BaF2 detectors ( = ±135°) with an
external magnetic field (Bext = 0.3 T), we found that theoscillation pattern in Fig. 1 was due to the magnetic
hyperfine interaction, since the oscillation pattern obtained

2nd sample

-0.05

0.00
0

(1)

1st sample-0.05

A22G22(t)

PR3-5

5

10
15
t (ns)

20

25

Fig. 1. Room-temperature TDPAC spectra for two
samples of 140CeFe.

REFERENCES:[1] Y. Ohkubo, A. Taniguchi, Q. Xu, M. Tanigaki, N.
Shimizu, and T. Otsuka, Phys. Rev. C 87, 044324(2013).
[2] W. van Rijswijk, F. G. van den Berg, H. E. Keus, and W.
J. Huiskamp, Physica B+C 113, 127 (1982).

採択課題番号 24P3-4b 超イオン伝導体 AgI 中の放射性核での電気四重極相互作用 プロジェクト（京大・原子炉）大久保嘉高、谷口秋洋、谷垣 実（金沢大・理工研究域）佐藤 渉（金沢大院・
自然）水内理映子

PR3-6

Dispersion State of Al and Cd Impurities in ZnO

Graduate School of Natural Science and Technology,
Kanazawa University
1
Institute of Science and Engineering, Kanazawa University
2
Research Reactor Institute, Kyoto University

INTRODUCTION: Zinc Oxide (ZnO) doped withgroup 13 elements (Al, Ga, In) as impurity donors is expected to be applied to functional devices as n-type semiconductors. For a practical use of ZnO as a conduction-controlling device, it is of great importance to study
the physical and chemical states of the dilute impurity
ions in ZnO. The time-differential perturbed angularcorrelation method (TDPAC) is very suited for that purpose because it can directly provide atomic-level information of impurity atoms. In our previous TDPAC
studies, the 111Cd(←111mCd) probe has little interaction
with Al atoms doped in ZnO even at a high concentrationof 10 at.%, suggesting that Al impurities form some typesof aggregate [1,2]. In order to confirm the above inference, a TDPAC study was performed for ZnO doped with
Cd ions. Here, by a comparative study, more credible
information on the Al state of being is presented.
EXPERIMENTS:
For the synthesis of 2 at.%Cd-doped ZnO, stoichiometric amounts of cadmium oxide (CdO) and ZnO powder were mixed in a mortar for 2
h. The mixture was then pressed into a disk, and sintered in air at 1273 K for 3 h. About 3 mg of CdO enriched with 110Cd was irradiated with thermal neutrons ina pneumatic tube at Kyoto University Reactor, and radioactive 111mCd was generated by 110Cd(n,  )111mCd reaction. The neutron-irradiated CdO powder was thenadded into the 2 at.% Cd-doped ZnO powder, and mixedagain in a mortar for 20 min. The mixture was pressed
into a disk, and sintered in air at 1373 K for 45 min. A
TDPAC measurement was carried out for the 111Cd(←
111mCd) probe on the 151-245 keV cascade  rays with theintermediate state of I = 5/2 having a half-life of 85.0 ns.
RESULTS: Fig. 1 shows the TDPAC spectra ofCd(←111mCd) probe (a) in 2 at.% Cd-doped and (b) in
10 at.% Al-doped ZnO [2]. The directional anisotropy
on the ordinate,, was deduced from delayedcoincidence events of the cascade:111

A22G22 (t ) Here,

2 [ N ( , t )－N ( / 2, t )].
N ( , t )  2 N ( / 2, t )denotes the angular correlation coefficient,
the time-differential perturbation factor as a function of the time interval, t, between the relevant cascade-ray emissions, and N(,t) the number of the coincidence

events observed at angle, . From our previous TDPAC
measurement for undoped ZnO, it was found that the111
Cd(←111mCd) probe uniformly disperses in ZnO andoccupies the substitutional Zn site [3]. With respect toFig. 1(a), the spectral damping appears as a result of distribution of the quadrupole frequency  (= 12.2 (8)%).
Because the distribution is an index of diversity of thevicinity surrounding the 111Cd(←111mCd) probe, this experimental result shows that Cd ions are widely dispersed
in ZnO. On the other hand, in Fig. 1(b), the spectral
damping is less pronounced despite the presence of 10
at.% Al ions in the system ( = 7.4 (7)%), suggesting that
doped Al ions do not uniformly disperse in ZnO. We
found from these observations that doped Cd ions diffuse
into ZnO matrix and reside solely at the substitutional Zn
site, while Al ions disperse in ZnO in the form of considerably large aggregates of their own.

0.2
0.15

(a)

0.1
0.05

A22G22(t)S. Komatsuda, W. Sato1 and Y. Ohkubo2

0
0.2
0.15

(b)

0.1
0.05
0
-0.05
0

50

100 150 200 250 300

Time (ns)Fig. 1. TDPAC spectra of 111Cd(←111mCd)(a) in 2 at.% Cd-doped and (b) in 10 at.%Al-doped ZnO.

REFERENCES:[1] S. Komatsuda, W. Sato, S. Kawata, and Y. Ohkubo, J.
Phys. Soc. Jpn. 80, (2011) 095001.
[2] S. Komatsuda, W. Sato, and Y. Ohkubo, KURRI Progress Report 2010, (2011) 94.
[3] W. Sato, S. Komatsuda, and Y. Ohkubo, Phys. Rev. B
86, (2012) 235209.

プロジェクト
採択課題番号 24P3-5a
酸化亜鉛中の不純物が形成する局所構造観察（金沢大・理工研究域）佐藤 渉（金沢大院・自然）小松田沙也加（京大・原子炉）大久保嘉高

PR3-7

Irradiation Effect on the Formation of Defects in 57Co-Doped ZnO
Observed by the Mössbauer Spectroscopy

W. Sato, T. Suzuki1, Y. Kano1, T. Takahashi2, N. Abe2 and
Y. Ohkubo2
Institute of Science and Engineering, Kanazawa
University
1
Graduate School of Natural Science and Technology,
Kanazawa University
2
Research Reactor Institute, Kyoto University

INTRODUCTION: Zinc oxide (ZnO) is a promisingn-type semiconductor having an optoelectronic property.
It is also known that doping of a minute amount ofmagnetic element(s) such as Co, Fe, and Mn induces
dilute magnetism in the semiconductor, leading to future
spintronics devices. Apart from the impurity-induced
magnetism, damages brought about by the kinetic
implantation of impurity ions are also attracting attention
as another cause of magnetism [1]. According to Ref.
[1], the induced magnetism arises from lattice damages
produced around the dopants substituting for Zn.
However, there is another interpretation of theexperimental result that the induced magnetism is
ascribable to exchange interaction between impurity ions
implanted at a high dose. Thus, the origin of themagnetism is not yet unequivocal. The purpose of thepresent work is to examine the irradiation effect on thehyperfine field produced by defects presumably formed
around dilute magnetic ions doped in ZnO. In this work,
we introduced in ZnO the 57Co(→ 57Fe) probe of the
Mössbauer spectroscopy, and Mössbauer parameters
obtained before and after electron beam irradiation are
discussed.
EXPERIMENTS: Powder ZnO was pressed into a disc,and 57Co HCl solution was then added in droplets onto
the disc. For the diffusion of the radioactive ions, thesample was heated in air to perform a solid state reaction
at 1273 K for 6 h. The prepared sample was ground into
powder and measured by the emission Mössbauer
spectroscopy with the 57Co(→ 57Fe) probe. After the
spectrum was obtained, the sample was sealed in a quartz
tube in vacuum, and irradiated for 30 m with electronsand bremsstrahlung of the maximum energy of 19 MeV.
The average current of the pulsed electron beam at the
sample was approximately 150 A.
After theirradiation, an emission Mössbauer measurement wasagain performed for the sample.
RESULTS: The Mössbauer spectra of 57Co(→ 57Fe)
doped in ZnO measured at room temperature are shownin Fig. 1, and the Mössbauer parameters obtained by thefits are listed in Table 1. As shown in Fig. 1(a), thespectrum is made up of only one component exhibiting aquadrupole splitting. It was found from the Mössbauer

parameters that 57Co occupies the defect-freesubstitutional Zn site [1], where no internal magnetic
field is present. For the Mössbauer measurement for theirradiated sample, as is obvious with Table 1, littlechange was observed in the hyperfine parameters.
Besides, contrary to the inference from the reports [1,2],
local magnetism was not induced by the present
irradiation condition. This result implies the following
two possibilities: 1) the local structure surrounding theprobe is stable enough to preserve the chemical bonding
from the present irradiation, or 2) although the local
structure was indeed damaged once by the irradiation,
annealing effect has worked to repair the damages
because of the room temperature irradiation. For further
information on the irradiation effect, low temperatureirradiation and/or measurement should be carried out.

Fig. 1. Mössbauer spectra of 57Co(→57Fe) doped in ZnO
measured at room temperature (a) before and (b) after
irradiation with electrons and bremsstrahlung.
Table 1. Mössbauer parameters obtained for 57Co-doped
ZnO at room temperature. The alphabetical notation forthe sample has the same meaning as that in Fig. 1.
Sample(a)(b)

I. S. (mm/s) Q. S. (mm/s)
0.78 (1)0.39 (1)0.81 (1)0.33 (1)

Bhf (T)——

REFERENCES:[1] G. Weyer et al., J. Appl. Phys. 102 (2007) 113915 (1 –7).
[2] R. Sielemann et al., Phys. Rev. Lett. 101 (2008)
137206 (1 – 4).

プロジェクト
採択課題番号 24P3-5b
酸化亜鉛中の不純物が形成する局所構造観察（金沢大・理工研究域）佐藤 渉（金沢大院・自然）小松田沙也加（京大・原子炉）大久保嘉高

Mössbauer Study of a Parent Material of Fe-Based Superconductors, FeTe

S. Kitao1,2, M. Kurokuzu1,2, Y. Kobayashi1,2, R. Masuda1,
and M. Seto1,2,3
1Research Reactor Institute, Kyoto University
CREST, Japan Science and Technology Agency
3
Japan Atomic Energy Agency
2

INTRODUCTION: Since the discoveries of the
Fe-oxipnictide superconductors, LaFePO [1] andLaFeAsO1-xFx [2], extensive researches have been
performed to elucidate the mechanism of theirsuperconductivity. Among these and the successively
discovered related Fe-based superconductors, theso-called “11” series, such as FeSe [3], has the simplest
crystal structure.
However, different from thefirstly-found “1111” series, the magnetism of the parent
compound of “11” series, FeTe, shows a complicatedmagnetic structure [4]. Since it is believed that the Fe
acts as a key element and its magnetism must relate to thesuperconductivity, studies of their Fe magnetism is one of
the main issues to reveal its superconducting mechanism.
To investigate the nature of its magnetism,
57
Fe-Mössbauer spectroscopy is an essential method.
Until today, a number of Mössbauer studies on these
Fe-based superconductors have been carried out andrevealed many important facts for LaFeAsO1-xFx [5,6]and FeTe [7-9]. However, the complicated magnetismof FeTe has not thoroughly been understood yet. In thisstudy, the magnetic structure of FeTe was investigated byobtaining detailed temperature dependence of the
Mössbauer spectra.
EXPERIMENTS: A single crystal of FeTe0.9 wassynthesized from a stoichiometric mixture of reduced Fe
and distilled Te in a crucible of aluminum oxide sealed ina quartz tube. The tube was heated up to 1070°C in 24
h and cooled down to 710°C at a rate of 3°C/h, andannealed at 400 °C for 10 days. The obtained single
crystal was characterized by x-ray diffraction andmagnetic susceptibility measurements. 57Fe-Mössbauer
spectra were measured using a pellet of powdered FeTe0.9
using a 57Co source in Rh matrix with a nominal activityof 1.85 GBq. The velocity scales are referenced to
α-Fe.
RESULTS AND DISCUSSION: Typical Mössbauer
spectra for FeTe0.9 are shown in Fig. 1. The magnetictransition was clearly observed by the detailed
temperature dependence of the Mössbauer spectra. The
observed internal magnetic field reached around 10 T at
5K with a certain distribution, implying a complicatedmagnetic structure. The magnetic transition temperature
was determined to be around 70 K by the temperaturedependence of the internal magnetic fields.
Theobserved anisotropy of the magnetic spectrum clearly
indicates the existence of a quadrupole splitting in themagnetic ordered phase.
Since the value of thequadrupole splitting abruptly changes from that for thehigh temperature phase, this change is considered to be
due to a structural phase transition accompanied by themagnetic transition.
1.00
0.99

70K

0.98

1.00
0.99
0.98

290K

1.00

1.00

65K

0.99

150K

0.98

0.98

Transmission

PR3-8

1.00

1.00

60K

0.99

100K

0.98

0.98

1.00

1.00

20K

0.99

90K

0.98

0.98
1.00

1.00

5K

0.99

80K

0.98

0.98

FeTe0.9
-10

-5

0

5

10

-10

Velocity (mm/s)

Fig. 1.

-5

0

5

10

Velocity (mm/s)

Typical Mössbauer spectra for FeTe0.9.

REFERENCES:[1] Y. Kamihara, H. Hiramatsu, M. Hirano, R. Kawamura, H.
Yanagi, T. Kamiya and H. Hosono, J. Am. Chem. Soc. 128(2006)10012.
[2] Y. Kamihara, T. Watanabe, M. Hirano and H. Hosono, J. Am.
Chem. Soc. 130 (2008) 3296.
[3] F.C. Hsu, J.Y. Luo, K.W. Yeh, T.K. Chen, T.W. Huang, P.M.
Wu, Y.C. Lee, Y.L. Huang, Y.Y. Chu, D.C. Yan, and M.K.
Wu, Proc. Natl. Acad. Sci. USA.105 (2008) 14262.
[4]W. Bao, Y. Qiu, Q. Huang, M.A. Green, P. Zajdel, M.R.
Fitzsimmons, M. Zhernenkov, S. Chang, M. Fang, B. Qian,
E.K. Vehstedt, J. Yang, H.M. Pham, L. Spinu, and Z.Q. Mao,Phys. Rev. Lett. 102 (2009) 247001.
[5] S. Kitao, Y. Kobayashi, S. Higashitaniguchi, M. Saito, Y.
Kamihara, M. Hirano, T. Mitsui, H. Hosono and M. Seto, J.
Phys. Soc. Jpn. 77 (2008) 103706.
[6] S. Kitao, Y. Kobayashi, S. Higashitaniguchi, M. Kurokuzu,
M. Saito, T. Mitsui, Y. Kamihara, M. Hirano, H. Hosono
and M. Seto, J. Phys.: Conf. Ser. 217 (2010) 012120.
[7] J. Suwalski, J. Piekoszewski, and J. Leciejewicz, Proc. Conf.
Appl. Möss. Effect 1969, p 385.
[8] Y. Mizuguchi, T. Furubayashi, K. Deguchi, S. Tsuda, T.
Yamaguchi, and Y. Takano, Physica C 470 (Suppl. 1) (2010)
S338.
[9] A. Błachowski, K. Ruebenbauer, P. Zajdel, E.E. Rodriguez
and M.A. Green, J. Phys. Cond. Matter 24 (2012) 386006.

採択課題番号 24P3-6
メスバウアー分光を用いた新規材料の物性研究（京大・原子炉）瀬戸 誠、北尾真司、小林康浩

プロジェクトPR3-9Study on Rapid Spin Equilibrium and Magnetic Phase Transition for(C6H5)4P[MnIIFeIII(C2O3S)3] by Means of High Field 57Fe Mössbauer Spectroscopy

N. Kojima, A. Okazawa, J. Yoshida, Y. Kobayashi1 and
M. Seto1

paramagnetic even at 24 K, and both of the MnII and FeIII spinsare eventually ordered at about 23 K.

Graduate School of Arts and Sciences, The University of Tokyo
1
Research Reactor Institute, Kyoto University

1

0.95
0.9
0.85

30 K

INTRODUCTION: In the case of assembled transition
metal complexes whose spin states are in the spin-crossover
region, concerted phenomena coupled with the spin-crossoverphenomenon and magnetic phase transitions are expected. From
this viewpoint, we have synthesized a mto (= C2O3S) bridged
hetero-metal complex, (C6H5)4P[MnIIFeIII(mto)3] (1-mto)
consisting of FeIIIO3S3 and MnIIO6 octahedra [1]. In this complex, it is expected that the internal magnetic field at the MnII site
is fluctuated by the rapid spin equilibrium at the FeIII site, which
influences the magnetic phase transition.
The molar magnetic susceptibility (χM) multiplied by thetemperature, χMT, is estimated at 6.90 cm3 K mol−1 at 400 K.
This value is in the middle of the spin-only values for the HS (S= 5/2) and LS (S = 1/2) states of FeIII, 8.75 cm3 K mol−1 and 4.75
cm3 K mol−1, respectively, implying that the spin equilibrium
occurs at the FeIIIO3S3 site. The χM as a function of temperature
has a broad maximum, a typical character of the 2D Heisenberg-type antiferromagnet, around 50 K, and shows a steep
increase below 30 K with a hump around 23 K. At 23 K, both
the real (’) and imaginary (”) parts in the AC magnetic susceptibility exhibit steep peaks indicating a magnetic phase transition. At 30 K, the remnant magnetization and the magnetic
hysteresis loop disappear. Therefore, it is obvious that 1-mto
undergoes two successive magnetic phase transitions at 30 K
and 23 K. In order to investigate the rapid spin equilibrium andmagnetic phase transition for 1-mto, we performed 57Fe
Mössbauer spectroscopy under high magnetic fields.
EXPERIMENTS:
The 57Fe Mössbauer experiments on
57
1-mto were carried out with a Co/Rh source cooled down to
200 K using a superconducting magnet at the magnetic field up
to 8 T. The magnetic field was applied parallel to the γ-ray direction. The spectra were calibrated by using the six lines of abody-centered cubic iron foil (α-Fe), the center of which wastaken as zero isomer shift.
RESULTS: Fig. 1 shows the 57Fe Mössbauer spectra of 1-mto
at 30 K, 22 K and 10 K. Despite the coexistence of HS and LS
states of FeIII, only a single doublet is observed between 300 and
30 K, which implies that the time scale of spin equilibrium between the HS and LS states is faster than that (10-7 s) of the 57Fe
Mössbauer spectroscopy between 300 and 30 K. At 30 K, despite the appearance of magnetic ordering, a single quadrupole
doublet indicating a paramagnetic phase is observed. As temperature is lowered, a drastic change of the spectral profile
caused by the internal magnetic field is seen between 23 K and
22 K, which reveals that the spin state at the FeIII site is still

Relative transmission

0.8
0.75
1
0.99
0.98

22 K

0.97
0.96
0.95

1
0.98
0.96
0.94

10 K

0.92
-10

-5

0

5

10

Velocity [mm/s]

Fig. 1. 57Fe Mössbauer spectra for 1-mto at 30 K, 22 K, and 10 K [1].

Fig. 2. Field dependence of the 57Fe Mössbauer spectra for 1-mto at 10
K (left). Hyperfine magnetic field distribution (right).

Fig. 2 shows the field dependence of the 57Fe Mössbauer
spectrum for 1-mto at 10 K. In general, the relative line intensityof the 57Fe Mössbauer line number of 2 and 5 depends on theangle, θ, between the Fe spin direction and the direction of the
γ-ray from the Mössbauer source. The average angle, θ, isexpressed as arccos{(4 – x) / (4 + x)}1/2, when the line intensity
ratio is written as 3 : x : 1 : 1 : x : 3. As shown in Fig. 2, the relative line intensity of the Mössbauer line no. of 2 and 5 increases
in the order of H = 0 T → 4 T → 8 T as follows, 3 : 2.1 : 1 : 1 :
2.1 : 3 → 3 : 2.9 : 1 : 1 : 2.9 : 3 → 3 : 3.2 : 1 : 1 : 3.2 : 3. The θincreases up to 70.1° with increasing external magnetic field up
to 8 T, which implies that the critical field of spin-flop transitionis higher than 8 T. Above the critical field, it is considered thatthe relative line intensity of the Mössbauer line no. of 2 and 5
decreases from 4 to 0 with increasing external filed. In order toinvestigate the anisotropic energy and the internal magnetic field,
the high-field 57Fe Mössbauer spectroscopy is indispensable andin progress.
REFERENCE:[1] K. Kagesawa, Doctoral Thesis (The University of Tokyo, 2011).

採択課題番号 24P3-7 集積型 Fe(III)錯体におけるスピン平衡の強磁場下 57Fe
プロジェクトメスバウアー分光研究（東大・院総合文化）小島憲道、岡澤 厚、吉田順哉（京大・原子炉）小林康浩、瀬戸 誠

PR3-10

Elucidation of a Correlation between Magnetic Properties and Host-Guest
Interactions in Porous Coordination Polymers

M. Ohba, R. Ohtani1, M. Arai1, S. Kitao2 and M. Seto2
Department of Chemistry, Faculty of Science, Kyushu
University
1
Graduate School of Engineering, Kyoto University
2
Research Reactor Institute, Kyoto University

INTRODUCTION:
Porous coordination polymers (PCPs) are a new type ofguest adsorbent material consisting of flexible coordination bonds to provide permanent and designable regularporous structures [1]. Such PCPs are expected to be
multifunctional platforms combining porous properties
with specific chemical and physical properties. To couple magnetic or redox properties and the porous properties we synthesized two novel Fe(II) PCPs,{Fe(dpa)[Pt(CN)4]G} (dpa = 1,2-di(4-pyridyl)ethane; G =dpa, stb (stilbene)) (1-G) and [Fe(isophthalate)(bpy)] (2).
Host-guest composites, 1-G accommodating some organic molecules as the guests, showed various spin transition (ST) behavior depending on the guest molecules.
1-dpa showed a sharp three-step ST in 150-200 K, on theother hand, 1-stb showed an abrupt one step ST. The
guest-dependent ST behavior of 1-G was explained byflexibility of the guest molecules. The multi-step ST of
1-dpa was confirmed by 57Fe-Mössbauer spectroscopy[2]. In the case of 2, an encapsulation of iodine molecules induced a host-guest redox behavior [3]. The donor property of 2 had a strong interaction with the electron accepter iodine to form the donor-acceptor complex.
EXPERIMENTS: 57Fe-Mössbauer spectroscopy wasmeasured to use a 57Co source with a nominal activity of
1.85 GBq. Velocity scale was calibrated as isomer
shifts relative to α-Fe.
RESULTS: As shown in Fig. 1, the Mössbauer spectrum of 1-dpa at 260 K consisted of a doublet peak withquadrupole splitting (∆Eq) (0.90 m s-1) and isomer shift(IS) (1.10 mm s-1) and a singlet peak with IS (0.51 mms-1), in which the isomer shift was based on the value of
α-Fe. These values of doublet and singlet peaks are
typical for FeII ions in the HS (S = 2) and the LS (S = 0)states, respectively. The proportion of the HS state decreased with decreasing temperature; 90.2 % (at 260 K),

Fig. 1. 57Fe-Mössbauer spectra of 1-dpa measured
at (a) 260 K, (b) 235 K, (c) 220 K, (d) 100 K in theheating process.
71.1 % (at 235 K), 53.6 % (at 220 K) and 13.3 % (at 100
K). The residual HS fraction at 100 K would be attributed to the generation of defects on the surface of
microcrystals. Different ST behavior of 1-stb were observed in Mössbauer spectra with IS of 0.46 (for singlet)and 1.15 (for doublet) and ∆Eq of 1.16 m s-1. These results suggested that a slight difference in guest molecule
greatly affects the magnetic behavior. In the case of 2,
all the iron species in the framework were determined to
be Fe2+ by Mössbauer spectra. The framework possesses
the electron donor property after degas treatment. 2
showed a permanent porosity and it adsorbed CO2, N2,
and O2 at 195 and 77 K. The donor property of 2 promoted the preferable iodine molecule insertion into thechannel. The iodine-containing 2 was characterized byvarious spectroscopies and X-ray technique, and these
elucidated that the half of Fe2+ were oxidized to Fe3+ andiodine were reduced. The hybrid of 2 and iodine showed
over 10-5 S/cm of electron conductivity.
REFERENCES:[1] S. Kitagawa et al., Angew. Chem. Int. Ed., 43 (2004)
2334-2375.
[2] R. Ohtani, M. Arai, S. Kitao, M. Seto, S. Kitagawa, M.
Ohba et al., J. Inorg. Organomet. Polym. Mater. 23(2013) 104-110.
[3] S. Horike, M. Sugimoto, S. Kitao, M. Seto, S. Kitagawa et al., J. Mater. Chem. A. 1, (2013) 3675-3679.

採択課題番号 24P3-8 多孔性金属錯体におけるホスト－ゲスト相互作用とプロジェクト磁気特性の相関の解明（九大院・理）大場正昭（京大院・工）大谷 亮、荒井将司（京大・原子炉）北尾真司、瀬戸 誠

PR3-11

Characterization of Gold Clusters Supported on Zinc Oxide by197
Au Mössbauer Spectroscopy

T. Yokoyama, Y. Okaue, D. Kawamoto, H. Ohashi1,
Y. Kobayashi2 and S. Kitao2
Faculty of Sciences, Kyushu University
1
Faculty of Arts and Science, Kyushu University
2
Research Reactor Institute, Kyoto University

INTRODUCTION: Gold nanoparticles supported onzinc oxide have been used as various oxidation-reduction
catalysts. It is essential to characterize the catalysts forunderstanding their advantages and establishing theguidelines for synthesizing catalysts with high activity.
For the characterization of supported gold catalysts, theiroxidation states have been determined by X-ray absortion
spectroscopy (XAS) and the crystal phases have been
detected by powder X-ray diffraction (XRD). However,supported gold catalysts have rarely been characterized
by 197Au Mössbauer spectroscopy.
In this study, the detailed chemical states of supported
gold catalysts were elucidated based on a combination of
XAS and 197Au Mössbauer spectroscopy.
EXPERIMENTS: Supported gold catalysts （Au/ZnO）
were prepared by the coprecipitation method. An aqueous
mixed solution of HAuCl4 and Zn(NO3)2 was poured into
an NaOH solution under stirring. The pricipitate was filtered, washed and freeze dried. The obtained materials
were calcined in air （Au/ZnO (air)） or were reduced ina flow of H2 gas （Au/ZnO (H2)） at 573 K for 4 h.
The chemical state of Au in the solid samples was determined by 197Au Mössbauer spectroscopy (home-madeequipment). 197Pt isotopes (T1/2 = 18.3 h), a γ-ray source
feeding the 77.3-keV Mössbauer transition of 197Au, wereprepared by neutron irradiation of isotopically enriched
196
Pt metal at the Kyoto University Reactor. The absorbers were the particle specimens. The source andspecimens were cooled with a helium refrigerator. The
temperature of the specimens was in the range 8 – 15 K.
The zero velocity point of the spectra was taken to be thepeak point for pure bulk gold. The spectra for all thesolid samples were each fitted with a single Lorentzianfunction.
Furthermore, for these catalysts, the Zn-K edge and
Au-L3 edge XAS were measured at BL14B2 ofSPring-8(Hyogo, Japan).

RESULTS:The Zn-K XANES spectra for the
Au/ZnO(air) and Au/ZnO (H2) catalysts revealed that Zn
was not reduced, unlike Ni in an Au/NiO (H2) catalyst.
The Au-L3 XANES spectra for the Au/ZnO (H2) catalyst
confirmed the presence of Au(0). However, the Au(0)was different from the bulk Au, suggesting a formation ofgold clusters. Fig. 1 shows the 197Au Mössbauer spectra
for the Au/ZnO catalysts. From the 197Au Mössbauer
spectrum for Au/ZnO (H2), it can be reasonably expectedthat relatively-uniform clusters were formed by hydrogen
reduction. After all, our established approach of the combination of XAS and 197Au Mössbauer spectroscopy [1] isquite useful to characterize supported gold catalysts.

Fig. 1. 197Au Mössbauer spectra for Au/ZnO catalysts and Au foil.

REFERENCE:[1] D. Kawamoto et al., Adv. X-Ray. Chem. Anal., Japan,
43, pp.293-302 (2012).

採択課題番号 24P3-9 メスバウアー分光による金触媒中の金化学種の状態分析（九大院・理）横山拓史、岡上吉広、川本大祐 （九大・基幹教育院）大橋弘範（京大・原子炉）小林康浩、北尾真司

プロジェクトPR3-12129

I Mössbauer Spectroscopy of AgI Nanoparticles

T. Yamamoto, K. Otsubo, H. Kitagawa, S. Kitao1 and
M. Seto1
Graduate School of Science, Kyoto University
1
Research Reactor Institute, Kyoto University

Solid-state ionic conductors
have been actively studied in many fields of scienceand technology because of their properties and application. Although liquid phases exhibit high ionic conductivity, solid-state ionic conductors are much moredesirable from the viewpoint of application for electrochemical devices such as batteries [1] and sensors(device fabrication, stability and safety). One of thehighest conductive ionic conductors is silver iodide(AgI) [2], which shows superionic conductivity greaterthan 1 S cm-1 in the high-temperature -phase [3].
Below 147 °C, AgI undergoes a phase transition into a
mixture of poorly conducting - and -phases, which
limits its application. Recently methods for the preparation of AgI nanoparticles have been reported andphase behavior has been investigated [4-7]. With decreasing nanoparticles size, the temperature of - to-/- phase transition shifts lower, for instance, the-phase survives down to 37 °C in 6.3-nm AgI nanoparticles. However, the origin of stabilization of the-phase is not clear. So, here we report 129I Mössbauer
spectroscopy of AgI nanoparticles, and discuss thecorrelation between stabilization and interaction ofinterface.
INTRODUCTION:

EXPERIMENTS: The sample used was synthesized
by the solution method. In order to avoid photoreductionof AgI, the synthesis was carried out with an apparatus
covered with aluminum foil. AgNO3 (0.067 mmol) andpoly-N-vinyl-2-pyrrolidone (PVP) K30 (1.243 mmol)
were dissolved in 60 mL of cold methanol and stirred at
the ice temperature for several minutes. Then 3.4 mL of
Na129I aqueous solution (1.61 Ci / mL) was added
quickly and stirred for 2 h. The synthesized sample wascollected by centrifugation and dried in air.
129
I Mössbauer spectroscopy on the synthesized sample
was performed at 13 K. 66Zn129Te was used as the -raysource, which was prepared by neutron irradiation of66
Zn128Te. The source velocity was calibrated by using
pure -Fe as the control material.
RESULTS: The observed data (dots) and the fitting
line are shown in Fig. 1. The fitting gives the hyperfine
interaction parameters (isomer shift IS, line width W,
quadrupole coupling constant QCC, and asymmetry parameter ). IS is 0.01 mm/s relative to the 66Zn129Te

Fig. 1. The 129I Mössbauer spectrum for AgI nanoparticles
using a Zn129Te source. The obtained hyperfine interaction
parameters are IS = 0.01 mm/s, W = 1.65 mm/s, QCC =-426.6 MHz, and  = 0.62.

source. The slightly large W value (1.65 mm/s) indicatesthat QCC has some distribution, and QCC is estimated at-426.6 MHz. Interestingly, the fitting gives better resultswith taking  as 0.62 rather than zero. From these parameters, it is supposed that the iodine in the AgI nanoparticles has a charge slightly more positive than -1, although that in bulk AgI has -1. It is conceivable that thischarge change derives from an interaction between thesurface of the nanoparticles and PVP. This strong interaction changes the surface energy of the nanoparticles,
which can result in stabilization of the -phase.
REFERENCES:[1] B. B. Owens, J. Power Sources, 90 (2000) 2-8.
[2] Z. Tubandt and E. Lorenz, Z. Phys. Chem., 87 (1914)
513-542.
[3] S. Hull, Rep. Prog. Phys., 67 (2004) 1233-1314.
[4] R. Makiura, T. Yonemura, T. Yamada, M. Yamauchi,
R. Ikeda, H. Kitagawa, K. Kato and M. Takata, Nat. Mater., 8 (2009) 476-480.
[5] S. Yamasaki, T. Yamada, H. Kobayashi and H. Kitagawa, Chem. Asian J., 8 (2013) 73-75.
[6] W. Sun, Y. Li, W. Shi, X. Zhao and P. Fang, J. Mater.
Chem., 21 (2011) 9263-9270.
[7] B. Xu and X. Wang, Small, 7 (2011) 3439-3444.

採択課題番号 24P3-10
ヨウ化銀ナノ粒子の相挙動の評価
プロジェクト（京大院・理）北川 宏、山田鉄平、大坪主弥、小林浩和、貞清正彰、山本貴之（京大・原子炉）
北尾真司、瀬戸 誠