VIII-Ⅱ-1. Project Research
Project 10PR10

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 radioactive nuclei.
This period is the first year of the project.
Unfortunately, the operation of the reactor was one week
delayed and moreover the operation time of the
KUR-ISOL was shortened because of some time taken to
fix a vacuum leak during the reactor operation.
The research subjects (PRS) executed in this period
are as follows:
PRS-1 Newly Available Fission Products at KUR-ISOL(II) (A. Taniguchi et al.).
PRS-2 Coincidence Summing Correction of Total
Absorption Clover Detector for Determination of -Ray
Intensities of Fission Products (M. Shibata et al.).
PRS-3 Half-Life Measurements of Excited Levels in
149
Nd (Y. Kojima et al.).
PRS-4 (a) Local Association of Aluminum Impurities
Doped in Zinc Oxide; (b) Irradiation Effect on theFormation of Defects in Silicon Observed by the
Positron Annihilation Spectroscopy (Y. Ohkubo et al.).
PRS-5 197Au Mössbauer Study of Au Nanoparticles (M.
Seto et al.).
PRS-6 Elucidation of a Correlation between Magnetic
Properties and Guest Inclusion in Magnetically Bistable
Porous Coordination Polymers (M. Ohba et al.).
PRS-7 Characterization of Gold Nanoparticles Supportedon Nickel Oxide by 197Au Mössbauer Spectroscopy:
Detection of Gold Alloy (T. Yokoyama et al.).
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 forheavy In isotopes and have confirmed that 126, 127, 128In
with half-lives of ~ 1 s (the heaviest stable isotope of In is
115In) were extracted with intensities enough for nuclear
spectroscopic experiments.
In order to obtain -ray intensities from fission
products, which are important data for decay heatestimation, Y. Shima et al. (PRS-2) determined the peakefficiency in the energy range of 50-3200 keV for their
total absorption clover detector composed of 4 large Ge
crystals by measuring singles and multiple -rays emitters.
The derived peak efficiency was found to agree with asimulated one using GEANT4, the coincidence summingcorrection having been done for the multiple -rays
emitters.

The half-life of the nucleus is one of clues tounderstanding nuclear structure. Using a radiation
detection system consisting of a high-purity Ge detector,
one thin plastic and one LaBr3 scintillators, Y. Kojima etal. (PRS-3) measured the half-lives of the 221-keV level,the 271-keV, and other three levels of 148Nd, its parent
148
Pr being obtained at KUR-ISOL: t1/2 (221-keV level) =1.60(4) ns and t1/2 (271-keV level) = 450(15) ps. The
former result is due to the slope method, and the latter
both the slope and centroid methods.
Zinc oxide, a semiconductor with a relatively large
band gap, has several favorable properties in materials
science. S. Komatsuda et al. (PRS-4a) took roomtemperature TDPAC spectra of 111Cd (←111In) introducedin 10 at.% and 10 ppm Al-doped ZnO, the patterns ofwhich are identical with each other. Together with the
XRD pattern of 0.5 at.% Al-doped ZnO, they concluded
that even ppm-level Al impurities formed ZnAl2O4.
Aiming at investigating the state of being and stabilityof impurities in semiconductors, W. Sato et al. (PRS-4b)
took room-temperature positron lifetime spectra forhigh-purity single-crystalline silicon wafers nonirradiatedand irradiated with -rays, and those irradiated withneutrons. They observed that a part of the positrons in the
Si irradiated with neutrons had a longer lifetime thanthose in the others.
Y. Kobayashi et al. (PRS-5) measured at 13 K the
197
Au-Mössbauer spectra for Au25(SG)18 (SG =glutathione) nanoparticles and those placed on a Au foil
in order to obtain information on the nature of the Au
atomic bonds in the nanoparticle and among thenanoparticles. They obtained the result implying that the
Au atomic bonds were weak or the nanoparticles moved
easily in the sample.
A porous coordination polymer, FeII(pz)[PdII(CN)4](pz = pyrazine), exhibits a spin transition near room
temperature with a hysteresis width of 20 K (Tc↑ = 304 K
and Tc↓ = 284 K). When iodine is included in the pores ofthe polymer as a guest, the hysteresis width increases 117
K. M. Ohba et al. (PRS-6) investigated the chemical
states of iodine using 129I-Mössbauer spectroscopy at 15
K on the iodine clathrate (low-spin state) and its analog
NiII(pz)[PdII(CN)4] (high-spin state). They obtained theresults indicating that the iodine interacted with various
sites in the pores and that its charge fluctuation originatedfrom different host–guest interactions.
As a characterization of supported gold catalysts, H.
Ohashi et al. (PRS-7) applied 197Au-Mössbauer
spectroscopy to obtain information of the chemical stateof gold nanoparticles supported on nickel oxide. From the
Mössbauer spectrum for Au/NiOx (H2), they consideredthat AuNix alloy phases were formed by hydrogen
reduction.

採択課題番号 23P10
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Newly Available Fission Products at KUR-ISOL (II)RESULTS: Fig. 1(a), (b) and (c) show the -ray energy
spectra for the mass number A = 126, 127 and 128, respectively. As seen in these spectra, the representative
-rays of 126In (T1/2 = 1.64 s and 1.60 s), 127In (T1/2 = 3.66
s and 1.09 s) and the daughter nuclide, and 128In (T1/2=
0.72 s and 0.84 s) were observed clearly. Thus, the ionization and extraction of 126, 127, 128In were confirmed.
CONCLUSION: In order to extend usable RI beams at
KUR-ISOL, ionization and extraction of indium isotopes

3

10

2

10

1

10

2

10

1

10

0

1141.11908.58

511

In

127

In
1597.7

10

126

(a)

(b)
128

1168.8

1

Sn)

10

127

2

491.3 (

10

511

3

831.5

EXPERIMENTS: Indium isotopes were obtained as
fission products of 50-mg 235UF4 irradiated at KUR-ISOL
under the 1 MW reactor operation. The produced fission
products were transported using the He/N2 gas-jet system
to the ion source. The ionized activities were
mass-separated using an electromagnet and collected on
an aluminized Mylar tape, and the yields were measured
by detecting representative -rays with a Ge detector of
about 30% relative efficiency. The Ge detector wasplaced at an in-beam position and the distance from thesource to the detector was 3 cm. The optimal values ofthe magnetic field for the indium ions were not known
although they could be estimated. Thus, the magnetic
field was increased stepwise (0.1 G/300 s) from the initialvalue for A ≈ 125 while monitoring -rays.

10

511

INTRODUCTION: For the studies of nuclear structure
and the application of radioactive-ion (RI) beams to otherfields, the variety, energy, intensity, etc. of usable RI
beams are important characteristics of RI beam facilities.
Here at KUR-ISOL (Kyoto University Reactor-Isotope
Separator On-Line), we are trying to extend usable RI
beams. In the previous period, we successfully obtained
beams of RI with sub-second half-lives, which are very
short for ISOL coupled to a gas-jet system like
KUR-ISOL [1]. In this period, ionization and extractionof indium isotopes in the neighborhood of a proton closed
shell Z = 50 was focused. Although it is considered thatindium atoms can be ionized using a surface ionization
type of ion source [2], which is adopted for KUR-ISOL,
it has never been attempted to extract indium isotopes at
KUR-ISOL and therefore their availability was unknown.

CountsResearch Reactor Institute, Kyoto University
1
School of Health Sciences, The University of Tokushima
Graduate School2
Radioisotope Research Center, Nagoya University

was tried by carefully tuning the magnetic field and theion source, and 126, 127, 128In beams were successfully obtained. The beam intensities were relatively strong andcould be enough for their nuclear spectroscopy experiments. Moreover, it might be possible to obtain a beam of
129
In, which is closer to a doubly magic nucleus (Z = 50,
N = 82) under the 5 MW reactor operation.

CountsA. Taniguchi, Y. Ohkubo, M. Tanigaki, H. Hayashi1, M.
M. Shibata2 and Y. Kojima2

Counts

PR10-1

In

(c)
500

1000

−ray energy (keV)

1500

Fig. 1. The -ray spectra for (a) A = 126, (b) A = 127
and (c) A = 128. Their representative -rays wereobserved. The magnetic fields for these spectra
were 3199 G, 3210 G and 3220 G, and the accumulation times were 20 min, 15 min and 5 min, respectively.

REFERENCES:[1] A. Taniguchi et al., KURRI Prog. Rep. 2010 (2011)
90.
[2] K. Blaum, Phys. Rep. 425 (2006) 1-78.

採択課題番号 23P10-1 オンライン同位体分離装置における生成・利用核種のプロジェクト多様化に向けた基礎研究（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（徳島大・医）林 裕晃

Coincidence Summing Correction of Total Absorption Clover Detector
for Determination of -Ray Intensities of Fission Products

Graduate School of Engineering, Nagoya University
1
Radioisotope Research Center, Nagoya University
2
Institute of Health Biosciences, The University ofTokushima Graduate School3
Research Reactor Institute, Kyoto University
INTRODUCTION: Precise nuclear decay data of fission products are important for the decay heat calculations. In our previous work, -rays following the decay of147
La were measured using a total absorption clover detector. We newly identified 56 excited levels from 1.0 to
3.5 MeV and 160 -rays [1], and demonstrated that thedetector was useful for the identification of high energy
levels and -rays. In this report, the peak efficiency of thedetector for a wide energy region was determined in order to deduce -ray intensities. We measured multiple
-ray emitters and determined the efficiencies corrected
for the coincidence summing based on the decay scheme
information. We verified that the coincidence summingcorrection was properly performed.
EXPERIMENTS AND SIMULATIONS: The detector has four large Ge crystals and a through hole along
the central axis of the detector. Radioactive sources canbe put into the through hole. In this measurement, two
spectra, a singles and an add-back spectrum, were obtained. In the singles spectrum, four individual spectra of
Ge crystals were summed and stored. In the add-back
spectrum, energy signals from the different crystals corresponding to coincident events were summed and thenstored. Peak efficiencies were determined using singles
spectrum.
The measurements were carried out as follows. First,
single -ray emitters of 54Mn, 109Cd, 137Cs and 203Hg (88 834 keV) were measured. A peak and a total efficiency
were calculated using the Monte-Carlo simulation code
GEANT4. In this calculation, the diameters and lengthsof Ge crystals were adjusted in order to reproduce theefficiencies obtained with the single -ray emitters. Next,
we measured multiple -ray emitters of 56Co, 133Ba and152, 154
Eu (53 - 3253 keV). The coincidence summingcorrection was applied for peak efficiencies obtained withthese nuclides. In order to absorb -rays, radioactive nuclides were sandwiched between a pair of 7-mm thickplastic -ray absorbers.
SUMMING CORRECTION: The summing correction was performed with the Monte-Carlo calculation
based on the decay schemes [2]. First, an excited level
where a -ray feeds was determined using -branchingratios. Second, decay paths of cascade -rays were simu-

採択課題番号 23P10-2

lated using -ray intensities, cascade relation of -rays
and conversion coefficients. In the electron capture decay
and the internal conversion processes, emission of fluorescence K X-rays was also taken into account, while
Auger electrons and other X-rays were neglected. Third,
interactions of each -ray or X-ray with the Ge crystals
were determined with the simulated peak and total efficiency. Consequently, we obtained two calculated spectra.
One is the spectrum with no coincidence summing effects.
The other is the spectrum including coincidence summing
effects. The correction factors were deduced by taking
the ratios of peak counts between the two spectra.
RESULTS: Fig. 1 shows the peak efficiencies of theclover detector. Crosses indicate the peak efficiencies
obtained with single -ray emitters. The simulated efficiency using the GEANT4 is shown by the solid curve.
The efficiency was in good agreement with those for the
single -ray emitters. The open and closed marks indicate
the experimental and corrected peak efficiencies obtainedwith the multiple -ray emitters. The corrected efficiencies were in agreement with the simulated efficiency
within 5%.
CONCLUSIONS: The coincidence summing correction was properly performed with the decay scheme information. The peak efficiency from 50 to 3200 keV wasdetermined using single -ray emitters, the Monte-Carlosimulation with the GEANT4 and multiple -ray emitterscorrected for the coincidence summing. A determinationof -ray intensities of 147La is now in progress.
100

Peak efficiency

Y. Shima, Y. Kojima 1 , H. Hayashi 2 , A. Taniguchi 3 and
M. Shibata 1(exp. - calc.) / calc. [%]PR10-2

152

Eu

154

Eu

133

Ba

56

Co
single -ray emitters
GEANT4

10-1

20
10-2
10

±5%

0
-10
-20
102

103

104

Energy [keV]

Fig.1. The full energy peak efficiency of the clover
detector.

REFERENCES:[1] Y. Shima et al., Proc. the 2011 Symposium on Nuclear Data, Tokai, Japan, Nov. 16-17, 2011, in press.
[2] Evaluated Nuclear Structure Data File (ENSDF),
http://nndc.bnl.gov/ensdf.

オンライン同位体分離装置を用いた核分裂生成物のプロジェクト
崩壊核データ測定（名大・RIC）柴田理尋、小島康明（名大院・工）嶋 洋佑（名大・工）永井悠太、山本晃一郎（徳島大・医）林 裕晃（京大・原子炉）谷口秋洋

Half-Life Measurements of Excited Levels in 149Nd

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 excited levels are oneof the most important properties in discussing nuclear
structure. In the previous works, we have developed a
new spectrometer consisting of a LaBr3 and plastic scintillation detector, and successfully obtained half-lives of
excited levels in 148Pr in a range of nanosecond using the decayed coincidence technique [1].
In this report, we present level half-life measurements for149
Nd in a range down to sub-nanosecond. The centroid
shift method was also applied to deduce short half-lives.
EXPERIMENTS: The 149Pr isotopes were prepared at
KUR-ISOL, following the thermal neutron-induced fission of 235U. The mass-separated beams were implanted
into an aluminized Mylar tape, and periodically moved toa measuring port. At the detector station, the LaBr 3, plastic scintillator and an HPGe detector were placed in aclose geometry. 1.7×108 events were accumulated in alist mode during a measuring period of 42 h.
RESULTS AND DISCUSSION: Fig.1(a) shows the
decay curve of the 221 keV level. It was obtained throughgating on the 112 keV -ray measured with the LaBr3
detector and on 109 keV -rays measured with the Ge
detector. A long slope is clearly observed in the spectrum.
From the least-squares fitting method using an exponential function, a half-life of 1.60(4) ns was deduced for thislevel. Our result agrees with the published half-life of
2.1(5) ns [2], having a much improved precision.
Fig.1(b) shows the time distribution obtained throughgating on the 162 and 109 keV -rays. From the slope,the half-life of 453(15) ps was derived for the 271 keVlevel. Here, it is generally agreed that the slope method
can deduce half-lives down to ~1/3 of time resolutions(FWHM) [e.g. 3]. Because the FWHM of our system is
550 ps for 165 keV, our results deduced from the slope
have sufficient reliability. Moreover, it is worthwhile analyzing the data on the basis of the centroid shift method,which enables half-life determination in a range down to~1/100 of FWHM in good statistical conditions [3].
Centroids were evaluated for time distribution curves
observed in the decay of 149Pr. As shown in Fig.2, most of
the centroids smoothly vary with the -ray energy. The
solid line shown in this figure is the best-fit quadratic
curve. We assume that this line represents the energy dependence of centroids of prompt time distributions. In

Fig.2, the centroid deduced from the decay curve of the
271 keV level was also plotted. The difference from theprompt curve corresponds to the mean lifetime of thelevel. From the centroid shift, the mean life of 560(95) ps(half-life of 390(65) ps) was deduced. It is in agreementwith the half-life of 453(15) ps obtained by the slope
method. The weighted mean of 450(15) ps was adopted
for the 271 keV level. This value is much smaller than theprevious value of 5.1(3) ns [4], which was deduced fromthe time distribution curve of the 162 keV -ray. The reason for this discrepancy is uncertain, but contribution due
to other levels or contamination of neighboring isotopes
in the previous work is possible explanation.
New half-life values for other 3 levels in 149Nd will also
be deduced from the centroids, while the data are notreported here because they are tentative. Further analysis
and discussion from the view point of nuclear physics are
now in progress.
CONCLUSIONS: Half-lives of excited levels in 149Nd
were measured using the LaBr3 detector in a range of afew hundreds picosecond.
(a)Counts per channel

Y. Kojima, Y. Shima1, H. Hayashi2, A. Taniguchi3 and
M. Shibata

10

T1/2=1.60(4) ns
2

10

1

10

0

(b)
10

3

10

2

T1/2=453(15) ps


271
221


1
10
109
109


0
0
149
149
Nd
Nd
0
10
1600 1650 1700
1580 1600
Channel number (122 ps/ch)



1620

Fig.1. (a) Decay curves of the 221 keV level and (b) 271
keV level in 149Nd. Gamma-rays gated by the LaBr3 detector
are shown by a thick arrows.
1580

centroid channel

PR10-31578

271 keV level

no 




271



109
0

1576
prompt curve
1574
0
200
400
600
800
−ray energy measured with LaBr 3 detector / keV

Fig.2. Centroids of time distribution curves observed in the-decay of 149Pr.

REFERENCES:[1] Y. Kojima et al., Nucl. Instr. Meth. A 659 (2011)
193-197.
[2] Evaluated Nuclear Structure Data File (ENSDF),
http://www.nndc.bnl.gov/ensdf.
[3] A. Schwarzschild, Nucl. Instr. Meth. 21 (1963) 1-16.
[4] R. Katajanheimo et al., Phys. Scr. 20 (1979) 125-128.

採択課題番号 23P10-3 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（名大・工）永井悠太、山本晃一郎（徳島大・医）林 裕晃（京大・原子炉）谷口秋洋

PR10-4

Local Association of Aluminum Impurities Doped in Zinc Oxide

S. Komatsuda, W. Sato1, S. Kawata2 and Y. Ohkubo3

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 dilute impurity ions in
ZnO, and for that purpose, the time-differential perturbed
angular correlation method (TDPAC) is very suited because it can directly provide atomic-level information of
impurity atoms. In our previous work, we made a successful observation that the 111Cd(←111In) probe is locallyassociated with Al ion(s) even at as extremely low concentration as 0.1 ppm of Al, while the 111Cd(←111mCd)
probe has little interaction with Al atoms doped at a highconcentration of 10 at.% [1, 2]. Our next interest is toelucidate the dispersion state of Al ions in ZnO. Taking
the above contrastive observations as a clue to the local
structure formed by Al impurities, in the present work,
we further investigated interacting nature between the111
Cd(←111In) probe and Al impurities doped in ZnO matrix. We here discuss local environment of Al atoms
based on the results of XRD and TDPAC measurements.
EXPERIMENTS: In this work, ZnO doped with two
different Al concentrations (10 ppm and 10 at.%) wereprepared. Stoichiometric amounts of Al(NO 3)3∙9H2O
and ZnO powder were mixed in ethanol. The suspension was heated to evaporate the ethanol until dryness.
The powders were pressed into disks and sintered in air at
1273 K for 3 h. An XRD measurement was performed
for one of the prepared samples doped with 10 at.% Al.
For TDPAC measurements, commercially available 111In
solution was added in droplets onto each of the sintereddisks with the different Al concentrations. The disks
again underwent heat treatment in air at 1373 K for 2 h.
The TDPAC measurements were carried out for the
171-245 keV cascade  rays of 111Cd(←111In) probe with
the intermediate state of I = 5/2 having a half-life of 85.0
ns.
RESULTS: Fig. 1 shows the TDPAC spectra of111
Cd(←111In) probe in (a) 10 at.% and (b) 10 ppm
Al-doped ZnO. The directional anisotropy on the ordinate,, was deduced with the following simple
operation for delayed coincidence events of the cascade:A22G22 (t ) 

2[ N ( , t )  N ( / 2, t )].
N ( , t )  2 N ( / 2, t )

(1)

Here,

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, . The spectral patterns
and the obtained nuclear quadrupole frequencies for both
samples are in good agreement with each other. These
results suggest that the local structures formed by the Al
ions at the probe sites are quite alike regardless of thelarge difference of Al concentrations. Meanwhile, as for
the XRD measurement for 10 at.% Al-doped ZnO, we
found that there emerged a spinel phase of ZnAl2O4 in
ZnO. Taking into account our previous observation that
the XRD pattern of 0.5 at.% Al-doped ZnO shows only
peaks corresponding to a wurtzite structure of ZnO [3],the present experimental results show that evenppm-level dilute Al impurities can locally associate witheach other to form such minute ZnAl2O4 grains that areundetectable within XRD detection precision.
-0.2

(a)

-0.15
-0.1
-0.05
0

A22G22(t)Graduate School of Natural Science and Technology,
Kanazawa University
1
Institute of Science and Engineering, Kanazawa University
2
Department of Chemistry, Faculty of Science, Fukuoka
University
3
Research Reactor Institute, Kyoto University

0.05

(b)

-0.15
-0.1
-0.05
0
0.05

0

50

100 150 200 250 300

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

REFERENCES:[1] S. Komatsuda et al., KURRI Prog. Rep. 2010 (2011)94.
[2] S. Komatsuda et al., J. Phys. Soc. Jpn. 80 (2011)
095001.
[3] W. Sato et al., Proc. Radiochim. Acta 1 (2011) 435.

採択課題番号 23P10-4
PAC を用いた金属酸化物中の超微細場の測定
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）小松田沙也加

PR10-5

Irradiation Effect on the Formation of Defects in SiliconObserved by the Positron Annihilation Spectroscopy

W. Sato, T. Togimitsu1, R. Ono1 and Y. Ohkubo2
Institute of Science and Engineering, Kanazawa
University
1
Graduate School of Science and Technology, Kanazawa
University
2
Research Reactor Institute, Kyoto University

INTRODUCTION: Positron annihilation lifetime
spectroscopy (PALS) is one of the most powerful tools
for the study on defects formed in various solid-statematerials. Among wide practical applications, thismethod is made use of especially for the estimation of theconcentrations, sizes, and types of lattice defects in suchmaterials as semiconductors and reactor materials. As
for semiconductors, lattice defects play important roles
for their electric conductivity; from this point of view, it
is of great importance to investigate the state of being andstability of impurities in semiconductors by means of thepresent spectroscopy.
As part of our impurity-related studies using
radiations as probes, we have started up research on
lattice defects in matter by the positron annihilation
method. In the present study, our interest was directedto lattice defects formed in single-crystalline silicon (Si)by radiation irradiation. Here, preliminary results ofdecay-rate change of positron annihilations caused byradiation damage are presented.
EXPERIMENTS: A 22Na (as in NaCl) positron source ofabout 3 MBq covered with a Mylar film was sandwichedwith high purity (99.999%) single-crystalline Si wafers
with a size of 14 × 14 × 0.5 mm3. The positronannihilation lifetime was measured with a conventional
circuit at room temperature, and BaF2 scintillators wereused for the detection of 1275- and 511-keV  rays.
After the measurement, the wafers were exposed to a-ray field at the absorbed dose rate in air of 2.76 kGy/hfor 48 h at the 60Co -ray irradiation facility of KURRI.
Aside from the exposure to the -ray field, an identical
type of Si wafers were irradiated for 1 h with thermal
neutrons at the fluence rate of 2.75×1013 cm-2 s-1 at KUR.
After the irradiations, PALS measurements were again
carried out for the Si wafers at room temperature. For
the analysis of the positron lifetime spectra, LT10
program was adopted [1].
RESULTS: In Fig. 1 is shown the PALS spectra obtained
for the Si wafers (a) nonirradiated, (b) exposed to the-ray field, and (c) irradiated with thermal neutrons. All
the spectra are made up of three different decay
components as numbered 1-3. The lines 4 stand for the
total of the three. Components 1 and 2 originate fromthe self absorption in the source materials: the Mylar
films and NaCl salt, respectively.
Component 3
corresponds to positron annihilations in the Si wafers. It
is obvious from the slopes of the decay curves ofComponent 3 that the lifetime of positrons in the Si
irradiated with neutrons are longer than the others. Thisobservational result should arise from the effect ofradiation damage caused by the neutron irradiation. We
thus further decomposed the component into two
different ones. Including the subcomponents, lifetimes
obtained for Component 3 are listed in Table 1. The
longevity of the positrons in the Si irradiated withneutrons could be attributed to their trap in vacancies
formed, for instance, by the recoil effect of the (n, )
reactions. As for the Si exposed to the  rays of 60Co,
however, little change was observed in the decay rate.
This may be because the energies of the relevant  rays
would not be enough to cause radiation damages
irrecoverable.

Fig. 1. Room-temperature positron lifetime spectra for single
crystalline silicon (a) nonirradiated, (b) exposed to the -ray
field of 60Co, and (c) irradiated with thermal neutrons. See thetext for each of the components 1 - 3.
Table 1. Lifetimes (ps) of positrons annihilated in the Si wafers.
See the text and Fig. 1 for the alphabetic symbols (a)-(c).

Subcomponents in Si
Bulk
Defect(a)209 (1)—(b)
213 (1)—(c)
209 (1)332 (2)

REFERENCE:[1] J. Kansy, Nucl. Instr. Meth. Phys. Res. A 374 (1996)
235 - 244.

採択課題番号 23P10-4 PAC を用いた金属酸化物中の超微細場の測定
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）小松田沙也加

Au Mössbauer Study of Au Nanoparticles

EXPERIMENTAL PROCEDURE:
Nanoparticles Au25(SG)18 (SG: glutathione) wereprepared by reduction of Au ions and refined byelectrophoreses [1]. Glutathione works as a surfactant
to avoid the fusion of nanoparticles.
For 197Au
Mössbauer measurements, the -ray source was 197Pt in Pt
foil, which was prepared by the 196Pt(n, )197Pt reaction
using KUR. The spectroscopy measurements were
performed at 13 K.
In the spectra, zero-velocity
positions were defined as the peak position for pure Au.
RESULTS AND DISCUSSION:
Fig. 1 (a) shows the 197Au Mössbauer spectrum for theAu25(SG)18 nanoparticles. The spectrum is composed of
3 subspectra.
Subspectrum 1 that shows a large
quadruple splitting is due to the Au atoms making chainswith the S atoms of glutathione on the surface of thenanoparticle.
Subspectrum 3 shows no quadruple
splitting, thus this subspectrum comes from the Au atoms
that are in the core of the particle. Subspectrum 2,which is due to the Au atoms covering the core, shows arather small quadruple splitting. The area ratio among
these components is consistent with the structure of thenanoparticle [2, 3].
For the recoilless fraction determination, we measured
the Mössbauer spectrum for the nanoparticles placed on
Au foil, and obtained the absorption area ratio between
the nanoparticles sample and the pure Au foil by fitting
the spectrum. Fig. 1 (b) shows the 197Au Mössbauer
spectrum of the Au nanoparticles placed on a 2.5 mthickness Au foil. The amount of Au in the nanoparticle
sample was 46 mg, and this sample was filled in a 7 mm

CONCLUSION:
The 197Au Mössbauer spectra for Au25(SG)18 nanoparticles consist mainly of three components, and the area
ratio of the three components shows a good agreementwith a structural model. The recoilless fraction of theAu25(SG)18 nanoparticles is only 9% for pure Au metal.

Subspectrum 3

10.18

10.17
6

INTRODUCTION:
Metallic nanoparticles are interesting in their peculiar
properties. We performed a 197Au Mössbauer study toelucidate the structure and the electronic state of Au
nanoparticles.
In this study, we found that the
Mössbauer absorption of nanoparticles is very small.
The fraction of the Mössbauer absorption is proportional
to the product of the absorber’s thickness and therecoilless fraction.
The recoilless fraction is theprobability of the Mössbauer absorption, which depends
on the bond strength of the Mössbauer atoms.
Thus,
we closely measured the Mössbauer absorption ratio of
nanoparticles to elucidate the atomic bond of Au
nanoparticles.

x10

Research Reactor Institute, Kyoto University
1
Graduate School of Science, Kyoto University
2
Department of Applied Chemistry, Tokyo University of
Science3
Department of Chemistry, The University of Tokyo
4
Graduate School of Arts and Sciences, The University ofTokyodiameter sample case.
Thus, the Au nanoparticle
sample is equivalent to a 62 m thickness Au foil.
The
ratio of Au thickness between the nanoparticle sample
and the Au foil is 25:1. In the observed spectrum, theabsorption area for the pure Au is 31%, so the ratio of theabsorption area is 2.2:1. This result means the recoilless
fraction of the nanoparticles is very small, which is only
9% for the pure Au metal. The small recoilless fraction
implies that the Au atomic bonds are weak or thenanoparticles move easily in the sample. To elucidate
the reason for this small absorption, we are planning tomeasure the absorption ratio for different size
nanoparticle, and compare it to the present result.

10.15

Subspectrum 1

(a)

10.16

CountsY. Kobayashi, S. Kitao, M. Kurokuzu1, M. Saito1, Y.
Negishi2, T. Tsukuda3, N. Kojima4 and M. Seto

Au25SG18

Subspectrum 2

7.42

6

197

x10

PR10-6

7.40(b)
Au foil

Au25SG18 + Au foil

7.38
-10

0

Velocity mm/s

10Fig. 1. 197Au Mössbauer spectra for (a) Au25(SG)18
nanoparticles and (b) Au25(SG)18 nanoparticles
placed on a 2.5 m thickness Au foil.

REFERENCES:[1] Y. Negishi, K. Nobusada, T. Tsukuda, J. Am. Chem.
Soc. 127 (2005) 5261.
[2] K. Ikeda, Y. Kobayashi, Y. Negishi, M. Seto, T. Iwasa,
K. Nobusada, T. Tsukuda, N. Kojima, J. Am. Chem.
Soc. 129 (2007) 7230.
[3] T. Tsukuda, Y. Negishi, Y. Kobayashi, N. Kojima,Chem. Lett. 40 (2011) 1292-1293.

採択課題番号 23P10-5 メスバウアー分光による新材料研究
プロジェクト（京大・原子炉）瀬戸 誠、小林康浩、北尾真司（京大院・理）黒葛真行、齋藤真器名PR10-7

Elucidation of a Correlation between Magnetic Properties and Guest Inclusion
in Magnetically Bistable 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 of guest adsorbent material consisting of flexible coordination bonds to provide permanent and designable regular porous structures [1]. Such
PCPs are expected to be multifunctional platforms combining porous properties with specific chemical andphysical properties. To couple the magnetic properties
and the porous properties we have researched PCPs exhibiting spin transition (ST). {FeII(pz)[PdII(CN)4]} (1;pz = pyrazine) shows ST near room temperature with ahysteresis width of 20 K (Tc↑ = 304 K and Tc↓ = 284 K).
The ST behavior of 1 could be controlled through guest
inclusion [2]. An iodine clathrate 1I was obtained byexposing the guest–free compound 1 to iodine vapor.
1I exhibited ST with a hysteresis width of 117 K (Tc↑ =320 K and Tc↓ = 203 K), which means drastic enhancement of cooperativity by the iodine inclusion. To elucidate the mechanism of the enhancement cooperativity, weinvestigated the chemical state and distribution of iodine
molecules in the pores by 129I-Mössbauer spectroscopy.
Because 129I-Mössbauer spectroscopy is available below
80 K due to effect of large lattice vibration, the spectrumof 1I in the high spin state cannot be obtained. For
deeper discussions, a nickel analog {NiII(pz)[PdII(CN)4]}(2) and its iodine clathrate (2I) having corresponding
frameworks to 1 and 1I in the high spin state were prepared as alternate samples.

diffraction patterns. The spectrum of 1I was simulated with three kinds of octuplets, indicating that threechemically independent iodine sites existed in the pores.
Site 1 had slight positive charge (IS = 0.95 mm s-1, QCC= -2540 MHz) with occupancy of 14.5 %. Site 2 was amain component with neutral charge (IS = 1.00 mm s-1,
QCC = -2290 MHz) and occupancy of 76.3 %. Site 3
was a minor component having slight negative charge (IS= 0.68 mm s-1, QCC = -1660 MHz) and occupancy of
9.2 %. Total charge of iodine was zero. Most of theiodine existed as I2 and a part of the iodine showedcharge separation in the pores of 1I.
These results suggested that the iodine molecules interacted with various sites in the pore and showed a charge
fluctuation originated from different host–guest interactions. The enhancement of cooperativity in 1I could
be explained by the change of interactions between iodine and framework associated with the ST.

EXPERIMENTS: 1I and 2I included 129I wereprepared by using 129I2 produced by heating to Pd129I2.
129
I-Mössbauer spectroscopy was measured to use
Zn129Te as radiation source at around 15 K under He atmosphere.
RESULTS: As shown in Fig. 1, 2I showed broader
peaks in comparison with the spectrum of 1I, indicatingthat the iodine existed at many sites with wide distribution in the pores incommensurately. In the high spinstate, each iodine molecule was affected by the different
environments of the pore surface and gave the broad
spectrum with diverse values of isomer shift (IS) and
quadrupole coupling constant (QCC). On the other
hand, 1I in the low spin state gave a narrow spectrum
because these iodine molecules were fixed in the porescommensurately. The different arrangement of iodine
between 1I and 2I was confirmed by X-ray powder

Fig. 1. 129I-Mössbauer spectra of (a) 1I in the low
spin state and (b) 2I corresponding to the framework in the high spin state at 15 K; observed (dots)
and simulation (line).
REFERENCES:[1] S. Kitagawa et al., Angew. Chem. Int. Ed. 43 (2004)
2334-2375.
[2] M. Ohba et al., Angew. Chem. Int. Ed. 48 (2009)4767-4771.

採択課題番号 23P10-6 磁気双安定な多孔性金属錯体における磁気特性とプロジェクト
ゲスト分子の相関の解明（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

Characterization of Gold Nanoparticles Supported on Nickel Oxide by 197Au
Mössbauer Spectroscopy: Detection of Gold Alloy

T. Yokoyama, Y. Okaue, D. Kawamoto, H. Ohashi1 and Y.
Kobayashi2
Faculty of Sciences, Kyushu University
1
Center for Research and Advancement in Higher Education, Kyushu University
2
Research Reactor Institute, Kyoto University
INTRODUCTION: Gold nanoparticles supported onnickel oxide have been used as various oxidation-reduction catalysts [1]. It is essential to characterize the catalysts for understanding their advantages andestablishing guidelines for syntheses of catalysts withhigh activity. For the characterization of supported gold
catalysts, the oxidation states of the supported gold nanoparticles have been determined by X-ray absorption
spectroscopy (XAS) and their 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 state of a supported gold catalyst was found using 197Au Mössbauer spectroscopy, in addition to the oxidation states and structuresof various metals having been obtained by XAFS.
EXPERIMENTS:
Supportedgoldcatalysts（Au/NiOx） were prepared by the coprecipitation method.
An aqueous mixed solution of HAuCl4 and Ni(NO3)2 waspoured into an NaOH solution under stirring. The
pricipitates were filtered, washed and freeze dried. The
obtained materials were calcined in air （Au/NiOx (air)）or were reduced in a flow of H2 gas （Au/NiOx (H2)） at
573 K for 4 h.
The chemical state of gold in the solid samples obtained was determined by 197Au Mössbauer spectroscopy(home-made equipment). The 197Pt isotope (T1/2 = 18.3h), a γ-ray source feeding the 77.3-keV Mössbauer transition of 197Au, was prepared by neutron irradiation of
isotopically enriched 196Pt metal at the Kyoto University
Reactor. The absorbers were particle specimens. The
source and specimens were cooled with a helium refrigerator. The temperature of the specimens was in therange 8 – 15 K. The zero velocity point of the spectra
was the peak point of pure bulk gold. The spectra for all
the solid samples were fitted with a single Lorentzianfunction.
Furthermore, for these catalysts, Ni-K edge and Au-L3
edge XAFS were measured at BL14B2 of SPring-8 (Hyogo, Japan).

reduced to nickel metal. The Au-L3 XANES spectra for
the Au/NiOx (H2) catalyst confirmed the presence ofAu(0). However, the Au(0) was different from bulk Au,
suggesting the formation of new phases. Fig. 1 shows
the 197Au Mössbauer spectra for the Au/NiOx catalysts.
From the 197Au Mössbauer spectrum for Au/ NiOx (H2), it
can be reasonably expected that AuNix alloy phases wereformed by hydrogen reduction [2].
The combinationof XAS and 197Au Mössbauer spectroscopy is quite usefulto characterize supported gold catalysts.

Au(OH) 3

Normalized Relative Transmission

PR10-8

Au/NiOx (H2)

Au/NiOx (air)Au foil-100Velocity / mm s-1

10

Fig. 1. 197Au Mössbauer spectra for the Au/NiOx
catalysts.
REFERENCES:[1] H. Nishikawa et al., Adv. X-Ray. Chem. Anal. Jpn. 43(2012) 285-292.
[2] D. Kawamoto et al., Adv. X-Ray. Chem. Anal. Jpn. 43(2012) 293-302.

RESULTS: The Ni-K XANES spectra for the Au/NiOx(H2) catalyst revealed that most of the nickel oxide was

採択課題番号 23P10-7 メスバウアー分光による吸着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

プロジェクト