Ⅲ-3
Chemistry
ChemistryBL1UⅢ -3. Chemistry

BL1U

Tracking Few-Femtosecond Auger Decay by Synchrotron Radiation
T. Kaneyasu1, Y. Hikosaka2, M. Fujimoto3,4, H. Iwayama3,4 and M. Katoh5,3SAGA Light Source, Tosu 841-0005, Japan
Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
The Graduate University for Advanced Studies, SOKENDAI, Okazaki 444-8585, Japan
5
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan1

2

The sequential interaction of a pair of timeseparated pulses with an atomic or molecular system
results in quantum interference between the resulting
atomic/molecular wave packets. In this work, we use
the recently disclosed ability of synchrotron lightsources to perform wave packet interferometry
experiments [1,2]. By using soft x-ray radiation wave
packets with attosecond-controlled spacing, we
observed the time-domain interferogram due to theinterference between electron wave packets launchedfrom the inner-shell 4d orbital of the Xe atom [3]. The
time-domain approach presented here enables us tocontrol the quantum interference in atomic inner-shellprocesses and to track the femtosecond decay of theshort-lived excited state.
The experiment was carried out at beamline BL1U.
The light source of BL1U consists of twin APPLE-II
undulators. The electrons passing through theundulators emit pairs of 10-cycle radiation wave
packets [Fig. 1]. The temporal duration and spectral
width of the radiation wave packets were about 2 fs and
3 %, respectively. The peak photon energy of the 3rd
harmonic radiation was adjusted close to the energy of
the 4d5/2-16p resonance. In order to monitor the
population of the 4d5/2-16p excited state, we detectedvisible fluorescence photons of 460-nm-wavlength
emitted from singly-charged ionic states formed via
spectator resonant Auger decay.
Figure 2(a) shows the fluorescence yields measured asa function of time delay over a range from 0 to 21 fs. The
time spectrum shows rapid oscillations, with a period of
approximately 63 as. This can be understood as “timedomain Ramsey fringes”, which arise from the quantum
interference of electron wave packets launched at
different times. Here the oscillation period corresponds tothe transition frequency of the Xe 4d5/2-16p inner-shell
excited state.
It is clear that the amplitude of the Ramsey fringes
decreases with increasing time delay. This can be
explained by considering the time evolution of the firstelectron wave packet during the sequential interaction.
Assuming a 6 fs lifetime for the 4d5/2-16p state, the timedamped Ramsey fringe spectrum can be calculated.
Figure 2(b) shows the calculated spectrum, taking into
account the temporal resolution of the delay control.
The good agreement between experiment andcalculation confirms that the reduction in fringe
amplitude does indeed arise from the excited state

lifetime, proving the time-domain access to
femtosecond Auger decay processes. While thetemporal resolution in synchrotron experiments has
been thought to be limited by the electron bunch length,
the present study clearly shows that processes in much
shorter timescale can be accessed by the use of thelongitudinal coherence between radiation wave packets.

Ⅲ-3

Fig. 1. (a) Experimental scheme for wave packet
interferometry. (b) Energy level diagram of Xe atom.

Fig. 2. (a) Fluorescence yield measured as a function oftime delay. (b) Calculated spectrum. (c)-(e) Comparison
between the experimental and calculated spectra.
[1] Y. Hikosaka et al., Nat. Commun. 10 (2019) 4988.
[2] T. Kaneyasu et al., Phys. Rev. Lett. 123 (2019)
233401.
[3] T. Kaneyasu et al., Phys. Rev. Lett. 126 (2021)
113202.

91

Ⅲ03- 1 -BL1U
Ⅲ -3. Chemistry

BL1U

Polarization Control in a Crossed-Undulator without a Monochromator
T. Kaneyasu1, Y. Hikosaka2, M. Fujimoto3,4, H. Iwayama3,4 and M. Katoh5,3SAGA Light Source, Tosu 841-0005, Japan
Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
The Graduate University for Advanced Studies, SOKENDAI, Okazaki 444-8585, Japan
5
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
1

2

Ⅲ-3

The crossed undulator scheme for synchrotron
radiation is a powerful method to produce light beams
of various polarization states. In this study, wedemonstrate that the polarization control of light froma crossed undulator can be achieved using the material
response, without any prior monochromatization [1].
Figure 1 compares the polarization control of lightfrom a crossed undulator by a conventional system andby the present method. A relativistic electron thatpasses though the undulators emits a pair ofhorizontally and vertically polarized radiation wave
packets which are separated by time delay τ. In a
conventional system, the radiation wave packets aretemporally stretched by a monochromator whichallows an interference between the two radiation fields.
Various polarization states can be obtained by tuning
the time delay using a phase shifter magnet that
controls the electron orbit between the two undulators.
On the other hand, when an atom is directly irradiatedby non-monochromatized radiation from the crossed
undulator, it absorbs specific frequency component.
Therefore, the resonant photoabsorption is expected toreflect the polarization determined by the interferenceof radiation fields at the resonant frequency.
A proof-of-concept experiment was performed at
BL1U. The light source of BL1U comprises a twin
APPLE-II undulators. The upstream and downstream
undulators were set in the vertical and horizontal linear
polarizations, respectively. The UVSOR-III synchrotron
was operated in the single bunch mode during themeasurements. The non-monochromatized undulator
radiation interacted with He atoms. The polarization
property of the light was investigated by observing the
Zeeman quantum beat in the fluorescence decay of the
1s6p 1P excited state [2]. Fluorescence photons with awavelength of 345 nm, which were emitted by the decay
from 1s6p to 1s2s states, were detected using aphotomultiplier tube equipped with a bandpass filter.
Figure 2 shows the fluorescence decay curves
measured at different setting of time delay. The
corresponding phase difference between the radiation
fields was tuned from π to 9π/2 with a step ofapproximately π/2. The shapes of beat structures change
according to the phase difference, reflecting thepolarization state of light. The observed beat structures
are well reproduced by the calculation curves. This
result verifies that polarization control in the crossed
undulator can be achieved using atomic response.

Fig. 1. Polarization control in a crossed undulator.

Fig. 2. Zeeman quantum beat measured for
fluorescence decay of 1s6p state. The gray circles andred curves represent measured and calculated results,
respectively. The polarization ellipse and vectors
assumed in the calculation are shown.

[1] T. Kaneyasu et al., New J. Phys. 22 (2020) 083062.
[2] Y. Hikoska et al., J. Synchrotron Radiat. 27 (2020)
675.

92

Ⅲ03- 2 -BL1U

Ⅲ -3. Chemistry

BL1U

Energy-Dependence of Photoelectron Circular Dichroism of
Chiral Molecules
H. Kohguchi1, Y. Hikosaka2, T. Kaneyasu3, S. Wada1, M. Fujimoto4, M. Katoh4
and Y-I. Suzuki5

Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526,
Japan
2
Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
3
SAGA Light Source, Tosu 841-0005, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
5
School of Medical Technology, Health Sciences University of Hokkaido, Tobetsu 061-0293, Japan1

Our group started a research project ofphotoelectron circular dichroism (PECD) of chiralmolecules with BL1U beamline in 2020 February.
Photoelectron scattering images exhibiting PECD,
which appears as forward-backward asymmetry of thephotoelectron angular distributions with respect to the
propagation direction of circularly polarized light forionization, have been measured for various typicalchiral molecules. Methyl oxirane is one of the typical
PECD molecules, by which we confirmed feasibilityof our experimental setup to measure PECD [1]. In thisresearch project, we have searched novel chiral species
showing PECD.
We conducted theoretical calculations based on
multiple scattering theory to predict the energydependence of PECD of polyaromatic molecules. The
theoretical results of some chiral systems yielded acertain amount of PECD parameters (β1) that aremeasurable with our experimental setup consisted of avelocity-mapping imaging (VMI) apparatus with theundulator light source at BL1U. Availability of samples
is practically important for PECD study since eachenantiomer is required for measurement. Most ofpromising candidates found in terms of theoretical β1
values and availability were solid compounds at room
temperature. We used a gas inlet nozzle with a heater tointroduce isolated chiral molecules into the vacuum
chamber. An example of the result (dimethyl
binaphthyl) is shown in Fig. 1; mass signals of thehigher mass > 60 amu with elevated nozzle temperatureserved as a good monitor for gas-phase samples in thedetection zone. The photoelectron signal with
irradiation of the VUV light increased as the growth of
the high-mass peaks, indicating photoionization of thechiral molecules. We obtained the photoelectron images
with a characteristic ring-like structure in the outerregion (Fig. 2). The multiple rings, which could
correspond to the band structure of the photoelectron
spectrum, disappeared at the higher photon energy. The
present experimental condition with linearly polarized
light is applicable to the circularly polarization
measurement. Additional calculation for the excited andionized electronic states will provide an solid
assignment of the photoelectron spectrum, which is afundamental spectroscopic data for PECD measurements.

Ⅲ-3
Fig. 1. Mass spectra of vaporized dimethyl binaphthyl
at several nozzle temperatures with a heat nozzle. (a)room temperature, (b) nominal nozzle temperature of
50 °C, (c) 80 °C.

Fig. 2. Photoelectron images of dimethyl binaphthyl atseveral ionization wavelengths: (a) hν = 11.0 eV, (b) hν= 12.3 eV, (c) hν = 12.5 eV, (d) hν = 15.5 eV (expanded).
White dotted circles define the detector edge.

[1] H. Kohguchi, Y. Hikosaka, T. Kaneyasu, S. Wada andY-I. Suzuki, UVSOR Activity Report 2019 47 (2020) 107.

93

Ⅲ03- 3 -BL1B,
Ⅲ -3. Chemistry

BL1B, BL6B

Low-Frequency and THz Region Spectroscopy on Various Organic
Molecules to Elucidate Microwave-Enhanced Organic Reactions
1

Ⅲ-3

H. Takaya1, K. Tanaka2, F. Teshima2, T. Yamada3, M. Nishioka4 and K. Kashimura4

International Research Center for Elements Science, Institute for Chemical Research, Kyoto University,
Uji 611-0011, Japan
2
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
3
Faculty of Science and Engineering, Keio University, Yokohama 223-8522, Japan
4
Faculty of Engineering, Chubu University, Kasugai 487-0025, JapanTHz and Low-frequency region spectroscopic
analysis was performed on various organic compounds
to investigate the dynamic behavior of organic
molecules under microwave (MW) irradiation.
MW-enhanced chemical process has been recently
focused intensely because the high-speed and highselective molecular conversion provide a highly
efficient chemical processes which never accessible byusing the conventional heating techniques such as oilbath and electric heater. In this research, we conducted
development of a BL1B/BL6B-based terahertz
spectroscopic system which can be used under
microwave irradiation to detect the molecular
dynamics under oscillating electromagnetic field.
Our research group found that various organic andinorganic reactions can be drastically accelerated
under microwave irradiation with high selectivity andlow energy consumption. For direct observation of theMW-induced molecular dynamics in these reactions by
THz spectroscopy at BL1B/BL6B, we designed a insitu THz measurement system as shown in Fig 1 (left),

where a newly developed small size MW resonantcavity is inserted into the optical path of sample
chamber of 1B. As shown in the picture of Fig 1 (right),
the setting of MW resonant cavity having a pair of lightpath port was succeeded to detect reference THz lightunder MW irradiation condition. We also designed
PEEK-made sample holder where a low-dielectric loss
factor material of PEEK is almost transparent toward
MW with negligible absorbance at 2.45 GHz
frequency of MW.
In the 2021 research project, we planed to performin situ THz spectroscopic experiments using thissystem to investigate the effects of microwaves on 1)
the racemization reaction of biaryl compounds where
the racemization proceeds intramolecularly throughthe rotation around the biaryl axial linkage and 2)
microwave-specific selective heating of nitrobenzenes
in toluene solution. First of all detection ofcharacteristic absorption bands (peaks) induced by
MW irradiation will be the main goals of this project.

Fig. 1. The layout of microwave reaction system in the measurement chamber of BL1B THz optic system (left)
and a picture of MW resonant cavity with the related electrical system inserted in the chamber of BL1B (right).

94

Ⅲ03- 4 -BL3U

Ⅲ -3. Chemistry

BL3U

XAS Measurements for Sugar Molecules in Aqueous Solutions
T. Sasaki and D. Akazawa

Department of Complexity Science and Engineering, Graduate School of Frontier Sciences,
The University of Tokyo, Kashiwa 277-8561, Japan
In recent years, attention has been paid to biomass
conversion using water or an ionic liquid as a solvent
without using an organic solvent. There have been
many studies on biomass-related compounds insolution, but there are few reports on their moleculartheory. We have studied the conversion process bydehydration reaction of polyalcohol as models of sugar
molecules and found that the solvation structure withwater molecules and the interaction with protons areimportant for the reaction process [1,2].
The purpose of this study is to explore the solvation
structure of sugar molecules in aqueous solution,
which is important in the conversion process fromcellobiose to glucose, that is typical of biomass
conversion process using water or ionic liquids.
Cellobiose, a disaccharide, is taken up as a model
substance for cellulose, which is one of the starting
materials in biomass conversion. Of these, cellobiose
can be hydrolyzed by the ionic liquid 1-ethyl-3methyl-imidazolium chloride (EmimCl) to produce
glucose [3]. These are typical routes for obtaining
useful compounds from cellulose. A typical biomass
conversion and utilization of glucose can be facilitatedby elucidating the solvation structures and conversion
mechanisms for related compounds.
In aqueous solutions, the dependence of temperature,pressure, and acidity will be investigated to elucidate
the roles of hydrogen bond networks and protons
surrounding sugar alcohol molecules. For ionic liquidaqueous solutions, the effect of polarity and viscosity
will be elucidated by investigating the ionic liquidcarbon chain length dependence. In this way, the entire
molecular mechanism of sugar alcohol conversion
using aqueous solutions and ionic liquid solutions will
be elucidated, and the possibility of a more efficientsugar alcohol conversion route will be explored.
XAS measurements for liquid samples wereconducted at UVSOR BL3U using facilities developed
by Nagasaka et al [4]. The liquid sample cell with
Si3N4 membranes was adopted, where the thickness of
the liquid layer was controlled by the He gas pressurearound the cell. The photon energy was calibrated byusing the C-K edge XAS spectrum of the proline thinlayer.
Figure 1 shows C-K edge XAS spectra for glucose
and cellobiose aqueous solutions with concentrations
specified in the figure. Molecular dynamics
calculations for the solutions and the XAS simulations
are under way to interpret the XAS spectra to explore
the solvation structures of sugar molecules.

C-K XAS of Glucose(aq)Intensity (arb. units)

1.00 M

0.50 M
0..10 M
0.05 M

0.01 M
282

284

286

288

290

292

294

296

Photon Energy / eV

Ⅲ-3
0.10 M

C-K XAS of Cellobiose (aq)Intensity (arb. units)

0.08 M

0.04 M

0.02 M

282

284

286

288

290

292

294

296

Photon Energy / eV

Fig. 1. C-K XAS spectra for glucose (upper panel)and cellobiose (lower panel) aqueous solutions.

[1] Y. L. Chang et al., J. Phys. Chem. B. 123 (2019)1662.
[2] T. Kondo et al., J. Compuational Chem. 42 (2021)
156.
[3] Vanoyle et al., Green Chem. 11 (2009) 390.
[4] M. Nagasaka et al., J. Electrosc. Relat. Phenom.
200 (2015) 293.

95

Ⅲ03- 5 -BL3U
Ⅲ -3. Chemistry

BL3U

Nitrogen K-edge X-ray Absorption Spectroscopy of Metal Protoporphyrin
IX Complexes in Aqueous Solutions
2

Ⅲ-3

M. Nagasaka1,2Institute for Molecular Science, Okazaki 444-8585, JapanThe Graduate University for Advanced Studies, SOKENDAI, Okazaki 444-8585, Japan
1

Iron porphyrin complex is a model of Cytochrome
P450 that is important for enzyme reaction such as
secondary metabolism. Chlorophyll a complex is used
as a light-harvesting antenna for photosynthetic
reaction. Thus, the electronic structural analysis of ametal complex is important for chemistry and biology.
X-ray absorption spectroscopy (XAS) in the hard Xray region extensively studied the electronic structuresof central metals in metal complexes during a metal toligand charge transfer process with photoirradiation[1]. The electronic structure of the central metal is also
investigated by Fe L-edge XAS (700 eV) in the soft Xray region [2]. Fe L-edge XAS is effective for theobservation of the interactions between central metals
and ligands since Fe L-edge is more sensitive for themeasurements of valence and spin states than Fe Kedge in the hard X-ray region [3]. On the other hand,
C and N K-edge XAS is necessary for investigating theelectronic structures of ligands in metal complexes.
Recently, Golnak et al. discuss the difference between
liquid and solid states of hemin, which is also known
as iron Protoporphyrin IX (FePPIX) complex, byusing N K-edge XAS in fluorescence yield [4]. In thisstudy, we have investigated interaction between metaland PPIX ligand from N K-edge XAS spectra of
FePPIX, CoPPIX, and PPIX complexes in aqueous
solution in transmission mode.
The experiments were performed by using atransmission-type liquid cell settled at BL3U [5]. The
liquid layer is sandwiched between two SiC
membranes and the liquid thickness is optimized toobtain appropriate absorbance of metal PPIX peaks.
50 mM FePPIX, CoPPIX, and PPIX in 0.5 M NaOH
solutions were prepared. Although these complexes
show dimer structure in aqueous NaOH solution, theinteraction between metal and ligand would not be
influenced in the dimer structures.
Figure 1 shows N K-edge XAS spectra of FePPIX,CoPPIX, and PPIX complexes in aqueous solutions.
Sharp peaks around 398 eV and 400 eV are observedin the spectra of PPIX complex. In CoPPIX complex,
the first peak shows a higher energy shift, and thesecond peak shows a lower energy shift compared tothose in PPIX complex. These peaks are overlapped in
the XAS spectrum. The XAS spectrum of FePPIX also
shows same spectral features although the shoulder at
the high energy side is smaller than that of CoPPIX.
The peak around 403 eV in PPIX complex is also
observed in CoPPIX complex, but it is not observed in
FePPIX complex. In the future, we will discuss themetal-ligand delocalization in metal PPIX complex
more precisely with the help of quantum chemical
inner-shell calculations.

Fig. 1. N K-edge XAS spectra of FePPIX, CoPPIX,and PPIX complexes with the molar concentration of 50
mM in 0.5 M aqueous NaOH solutions. The dashedlines indicate the peak positions of PPIX.

[1] C. J. Milne, T. J. Penfold, M. Chergui, Coord. Chem.
Rev. 277 (2014) 44.
[2] N. Huse et al., J. Am. Chem. Soc. 132 (2010) 6809.
[3] S. A. Wilson et al., J. Am. Chem. Soc. 135 (2013)
1124.
[4] R. Golnak et al., Phys. Chem. Chem. Phys. 17 (2015)
29000.
[5] M. Nagasaka, H. Yuzawa and N. Kosugi, Anal. Sci.
36 (2020) 95.

96

Ⅲ03- 6 -BL3U

Ⅲ -3. Chemistry

BL3U

XAS Study of a High Valent Oxo Species of a μ-Nitrido-Bridged Iron
Phthalocyanine Dimer Deposited on a Graphite Surface
Y. Yamada 1,2,3 and M. Nagasaka4

Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
2
Research Center for Materials Science, Nagoya University, Nagoya 464-8602, Japan
3
PRESTO/JST, Kawaguchi 332-0012, Japan
4
Institute for Molecular Science, Okazaki 444-8585, Japan

Methane has long been expected as a nextgeneration carbon resource because it is abundant innature as natural gas or methane hydrate. However, its
high C-H bond dissociation energy prevent thedevelopment of the catalyst that can convert methane
into more valuable raw chemicals under mild reaction
conditions. μ-Nitrido-bridged iron phthalocyanine
dimer 1 (Fig. 1) is one of a few molecular catalysts for
direct C-H activation of methane.[1,2] It is reported
that treatment of 1 with H2O2 in an acidic aqueous
solution produce high valent iron-oxo species 1oxo
possessing a strong methane oxidation activity.
However, the electronic structure of 1oxo have neverbeen investigated by XAS presumably because of its
high reactivity. In this study, we attempted to observe
1oxo directly by XAS by using a highly oriented
pyrolytic graphite (HOPG) substrate on which 1 was
deposited (1/HOPG in Fig. 2(a)). We assumed that 1oxo
generated on a HOPG substrate is stable enough for
XAS measurement as long as any organic substrates
do not coexist.
Beforehand of this study, we confirmed that 1 wasadsorbed on a highly oriented pyrolytic graphite toprepare 1/HOPG successfully by treatment of a HOPG
with the 1e–-oxidized monocationic species of 1 (1+)
in an organic solvent. O K-edge and Fe L-edge XAS
measurements were performed at the soft X-ray
beamline BL3U of UVSOR.[3] For thesemeasurements, 1/HOPG was fixed with double-sided
conductive carbon tape onto a stainless sample holder.
In order to generate 1oxo on HOPG substrate, 1/HOPG
was treated with 35% aqueous H2O2 just before
measurement. The holder with a HOPG sample was
fixed on a rotatable linear and installed into a vacuum
chamber (< 1 × 10−5 Pa). The XAS spectra were obtained
in total electron yields by measuring a sample draincurrent.
Figure 2b shows a comparison of the O K-edge XAS
spectra obtained for 1/HOPG and 1/HOPG treatedwith H2O2. It was found that the peak at around 532
eV was significantly increased after treatment with
H2O2. DFT calculation for 1oxo adsorbed on a graphenesuggested that the peak assignable to the excitation of
O1s – π* of Fe=O for 1oxo should appear at around 529
eV, whereas the peaks for 1 with a coordinating H2O
on a graphene were calculated to appear at higher than
534 eV as shown in Fig. 2(c). On the other hand, Fe Ledge XAS spectra of 1/HOPG after H2O2 treatment

showed slight high energy shifts compared to that
before treatment. Taking that 1oxo was observed by
MALDI-TOF MS by using 1/HOPG treated with H2O2,
it is considered that the spectra shown in Fig. 2
indicates that 1oxo was actually observed by XAS.

Ⅲ-3
Fig. 1. Formation of a high valent iron-oxo species
1oxo having methane oxidation activity.

(a)

N

(c)

N
N
N
FeNIII N
N
N

HOPG

1/HOPG(b)

Intensity / a.u.

N
N
N
FeNIV N
N
N

0.020

0.000

525

530

535

540

Photon energy / eV

After H2O2
Treatment

OH2
N
N
N
N
FeNIII N
N
N

0.050

N

0.040

0.06
0.04
0.02

N

0.030

N
N
N
FeNIV N
N
N

0.020

0.010

0

0.000

–0.02
520

N

N

0.030

Before H2O2
Treatment

0.08

N
N
N
FeNIV N
N
N

0.010

0.12
0.10

N

0.040

N
N
N
FeNIV N
N
N

Oscillator strength

N

・ 0

O
0.050

N

Oscillator strength

1

525

530

535

Photon energy / eV

540

545

525

530

535

540

Photon energy / eV

Fig. 2. (a) Structure of 1/HOPG, (b) Comparison of O
K-edge XAS spectra of 1/HOPG before and after
treatment with H2O2. (c) DFT-calculated O K-edge
XAS spectra for 1oxo on a graphene surface (upper) and1(OH2) on a graphene surface (bottom).

[1] P. Afanasiev and A. B. Sorokin, Acc. Chem. Res. 49(2016) 583.
[2] Y. Yamada, K. Morita, N. Mihara, K. Igawa, K.
Tomooka and K. Tanaka, New J. Chem. 43 (2019) 11477.
[3] T. Hatsui, E. Shigemasa, N. Kosugi, AIP Conf. Proc.
705 (2004) 921.

97

Ⅲ03- 7 -BL3U
Ⅲ -3. Chemistry

BL3U

Mechanistic Investigation of Homogeneous Nickel-Catalyzed Organic
Reactions Based on Solution-Phase L-edge XAS
1

Ⅲ-3

H. Takaya1,2, M. Nagasaka2 and K. Kashimura3

International Research Center for Elements Science, Institute for Chemical Research, Kyoto University,
Uji 611-0011, Japan
2
Institute for Molecular Science, Okazaki 444-8585, Japan
3
Faculty of Engineering, Chubu University, Kasugai 487-8501, Japan

catalyst of NiCl2(PPh3)2 1 was prepared in an argonfilled glovebox, because the solution of ironcomplexes are quite sensitive to oxygen and water, andimmediately react to give iron oxide and hydroxide. The
XAS measurement was successfully carried out undera flow condition (flow rate: 50–200 μL/h) to give Ledge NEXAFS of 1 without the undesired baseline
shift by the static electricity (Fig. 2.). However, thepenetration of helium gas into the cell causing abubbling noise could not be perfectly controlled. To
solve this problem, Viton O-ring is changed to afluorosilicone polymer with improving the flow line
design and tube connection. This improved cell is
testing in 2021 experiment.

We have found that iron complexes of NiX2
(phospine) (X =Cl or Br) bearing various phosphine
ligands showed excellent catalytic activities toward
the coupling of organometallic reagents of Mg, B, Al,
and Zn with various aryl halides [1]. Such nickelbased catalysts for organic reactions alternative to theconventional precious metal catalysts has been
intensively investigated for the development of futuresustainable production of chemical compounds.
Solution-phase XAS analysis is highly useful for themechanistic study of iron-catalyzed organic reactions
to identify the catalytically active organoiron species
with their electronic and molecular structures, because
the conventional solution-phase NMR analysis cannot
be used due to the paramagnetic nature of organoiron
species along with the large paramagnetic shift andpeak broadening in NMR spectrum. L-edge XAS oftransition-metal catalysts has been expected to behighly useful to investigate the electronic structure of
3d orbitals which provide essential information to
elucidate how to work the catalyst. However, solutionphase L-edge XAS measurement is generally difficult
because the measurement has to be performed under avacuum condition where the solution sample isvaporized with vigorous boiling. In this project, we used
the specially designed flow-cell for the solution-phase Ledge XAS measurement of homogeneous organic
solution of nickel complex catalysts. In BL3U beamline,
a stainless-steel flow cell has been used for various
experiments, but we should carefully avoid
contamination of iron species from the environment.
For this reason Prof. Nagasaka newly designed andprepared PEEK-made flow cell bearing ultra-thin 100
nm Si3N4 membrane X-ray window (Fig. 1. left). The
solvent-resistant PEEK made body worked well withan excellent chemical resistance toward the variousorganic solvents such as THF, CH2Cl2, toluene, andbenzene, these often used in nickel-catalyzed coupling
reactions. However, the static electrical charge
generated by the frictional interactions between PEEK
wall and organic solvents caused undesired baseline
shifts in the NEXAFS spectrum. To solve this problem,a gold-made electrode was attached to the Si3N4
membrane with earth connection (Fig. 1. right). This
flow cell was introduced into the He-filled chamber
which inserted into the X-ray optics line, andconnected to a syringe pump through a Teflon tube.
The toluene solution samples of nickel phosphineFig. 1. Photos of the PEEK-made flow cell.

Fig. 2. Solution-phase L-edge XAFS spectrum ofNCl2(PPh3)2 in toluene.
[1] JP Patent 2020-016437 (Feb. 3, 2020).

98

Ⅲ03- 8 -BL3U

Ⅲ -3. Chemistry

BL3U

Complex Formation in Glycine Betaine Saline Solution Revealed by
the Deconvolution of Its Soft X-Ray Absorption Band
S. Ohsawa1, N. Fukuda1, H. Iwayama2,3, M. Nagasaka2,3 and K. Okada1,4

Graduate School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
2
Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies, SOKENDAI, Okazaki 444-8585, Japan
4
Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
1

Living cells adapt to various environments, such as
drought and high salinity, by regulating theconcentration of solutes termed osmolytes [1], because
an increase in extracellular salinity can cause water
efflux and cell shrinkage. Among the most common
organic osmolytes is glycine betaine. The amount ofglycine betaine has been found to correlate withexternal salinity for several shoots of halophytes [2]and for halophilic eubacteria [3]. Altering thehydration structure of glycine betaine by salt addition
presumably plays an important role in protecting thesecondary structure of proteins, but the molecularlevel understanding of the hydration structure is not
yet fully explored [4]. In this report O 1s absorption
spectra were recorded for various concentrations ofglycine betaine and sodium chloride, to extract thehydrated and bulk water components by a peakdeconvolution technique.
Photoabsorption spectra of the solutions in theoxygen K-edge region were measured on the soft X-ray
beamline, BL3U. A pair of windows made of thinsilicon nitride membrane was used for the sample cell.
The incident photon energy was calibrated to the peakat 530.88 eV of a polymer film [5]. Peak deconvolution
was applied to the 4a1 resonance band of water into fivecomponents: one for the water hydrated to anions, three
for the bulk water and one for the water hydrated tocations.
Figure 1 displays the peak area of the component for
the water hydrated to cations versus the concentrationof either glycine betaine or sodium chloride. The data
for the betaine- and NaCl-only solutions align linearly,
indicating the correctness of the present analysis. For
mixed solutions of glycine betaine and sodium chloride,the data are plotted for the set of the varying NaCl
concentration with the glycine betaine concentration
constant (blue) and for the set of vice versa (green). The
area for the former set decreases up to about 0.55
mol/dm3. The slope corresponds to the consumption of
about 1.5 times the NaCl concentration. The decrease inarea can be interpreted to be caused by the loss of watermolecules hydrated to the solute due to the strong
interaction between glycine betaine and sodium
chloride. Above 0.55 mol/dm3 the area keeps nearly
constant, which infers that different components of ion
pairs exist in the solution. The data in green color
behave similarly but have different slope. These results
show that depending on the salt concentration thebetaine·Na+ complex with varying composition from
2:1 to 1:2 exists in glycine betaine saline solutions. We
can therefore safely conclude that this provides theosmoregulation function in living cells against salinity.

Ⅲ-3

Fig. 1. Peak area of the water component hydrated tothe sodium cation or cationic part of glycine betaine
plotted against concentration.

[1] P. H. Yancey, M. E. Clark, S. C. Hand, R. D.
Bowlus and G. N. Somero, Science 217 (1982) 1214.
[2] R. Storey and R. G. Wyn Jones, Plant Sci. Lett. 4(1975) 161.
[3] J. F. Imhoff and F. Rodriguez-Valera, J. Bacteriol.
160 (1984) 478.
[4] S. Ohsawa, N. Fukuda, H. Iwayama, H. Yuzawa, M.
Nagasaka and K. Okada, UVSOR Activity Report 201846 (2019) 115.
[5] M. Nagasaka, H. Yuzawa, T. Horigome and N.
Kosugi, J. Elec. Spectrosc. Relat. Phenom. 224 (2018) 93.

99

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Ⅲ -3. Chemistry

BL4U

Analysis of One-dimensional Single-crystalline Cathode Materials for
Secondary Batteries by Scanning Transmission X-ray Microscopy
E. Hosono1,2,3, W. X. Zhang3,4, D. Asakura1,2,3, Y. Harada3,4, H. Yuzawa5 and T. Ohigashi5,6Global Zero Emission Research Center, National Institute of Advanced Industrial Science and Technology,
Tsukuba 305-8568, Japan
2
Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology,
Tsukuba 305-8568, Japan
3
AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory (OPERANDO-OIL),
National Institute of Advanced Industrial Science and Technology (AIST), Kashiwa 277-8565, Japan.
4
Institute for Solid State Physics, The University of Tokyo, Sayo 679-5148, Japan
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
6
School of Physical Sciences, The Graduate University for Advanced Studies, SOKENDAI, Okazaki 444-8585, Japan
1

Fig. 1. A STXM image of the LiMn2O4 singlecrystalline nanowire.

Intensity (a.u.)

Ⅲ-3

Development of innovative technologies for clean
energy devices is desired to realize sustainable society
with preventing global warming, and development ofhigh-performance secondary batteries for electricvehicle applications and grid introduction through largescale power storage in renewable energy power plants is
attracting much attention.
In secondary battery materials, when Li or Na ionsdiffuse into or out of the host crystal, the crystal axis
along the diffusion path becomes clearer. However, theredox reaction is still unclear. The electronic-structurechange in transition metals and oxygen of the host
crystal due to the insertion or extraction of Li or Na in
the single-crystal active material should be unveiled indetail. It is desirable to clarify the distribution of theelectronic state using a position sensitive analysis withhigh spatial resolution. The knowledge of Li or Na
diffusion with the electronic-structure change of the hoststructure is important for the understanding of cathodematerials for secondary batteries from a viewpoint ofbasic science.
These discussions are directly related to the crystal
structure change (volume change) and charge-discharge
cycle characteristics related with fast ionic diffusion. If
we clarify the battery characteristics from the electronic
state, we can establish a strategy for innovative material
design.
Here, we show a result of STXM for LiMn2O4 singlecrystalline nanowire. Figure 1 shows the STXM image
measured with an excitation energy of 525 eV. Nanowire
image of LiMn2O4 was obtained by STXM. An O Kedge absorption spectrum of a selected region is shownin Fig. 2. The pre-edge region from 528 to 534 eV isattributed to the Mn 3d-O 2p hybridization.
In the near feature, we will establish operando STXM
measurement system.

525

530

535

540

545

550

Photon energy / eV

Fig. 2. O K-edge absorption spectrum of a selected
region.

100

Ⅲ03- 10 -BL4U

Ⅲ -3. Chemistry

BL4U

Analysis of High Active Photocatalytic Materials by Scanning Transmission
X-ray Microscope
Y. Miseki 1,2, E. Hosono1,3,4, D. Asakura3,4, H. Yuzawa5 and T. Ohigashi5,6Global Zero Emission Research Center, National Institute of Advanced Industrial Science and Technology,
Tsukuba 305-8568, Japan
2
Research Center for Photovoltaics, National Institute of Advanced Industrial Science and Technology,
Tsukuba 305-8565, Japan
3
Research Institute for Energy Conservation, National Institute of Advanced Industrial Science and Technology,
Tsukuba 305-8568, Japan
4
AIST-UTokyo Advanced Operando-Measurement Technology Open Innovation Laboratory (OPERANDO-OIL),
National Institute of Advanced Industrial Science and Technology (AIST), Kashiwa 277-8565, Japan.
5
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
6
School of Physical Sciences, The Graduate University for Advanced Studies, SOKENDAI, Okazaki 444-8585, Japan1

The conversion of solar energy into chemical energy
by artificial photosynthetic reactions is being studied asa candidate technology for realizing a sustainable lowcarbon society. For the widespread use of thistechnology in society, it is important to establish design
strategy for innovative photocatalytic materials that are
significantly superior to the current performance. Since
the photocatalytic reaction proceeds by redox reaction
at the interface, it is necessary to establish appropriate
design method for the reaction field, especially
technology to control the crystallinity and crystal planeof the material.
However, since each catalytic material has adifferent active surface, it is important to confirm
which surface is the active surface, as a preliminary
step for precise control. Comparing the electronic
states of the active surface with those of other surfaces
andelement-selectively/orbital-selectively
understanding the mechanism of high activity is
expected to lead to design strategy for the development ofinnovative materials.
To establish the high-level crystal growth techniquesand morphology control methods, theoreticalunderstanding from a viewpoint of electronic structureby using synchrotron radiation soft X-rays is necessary.
Scanning Transmission X-ray Microscope (STXM) is
most suitable to reveal the electronic structure
information with spatial information (minimum spatial
resolution is ca. 30 nm).
We have tried the preparation of operando
measurement system for crystal growth in STXM.
Figure 1 shows the optical microscope image of Mn2+
solution with agar gel sandwiched by Si chips with
Si3N4 windows. One of the major features of STXM isthat it is possible to obtain a spectrum of the solution by
sandwiching it between the Si3N4 windows.
Figure 2 shows the spectrum of Mn. In the nearfeature, we will establish in-situ measurement system.

Ⅲ-3

Intensity (a.u.)

Fig. 1. Optical microscope image of Mn solution withagar gel.

630

635

640
645
650
Photon energy / eV

Fig. 2. Absorbance spectrum of Mn.

101

Ⅲ03- 11 -

655

660

BL4U
Ⅲ -3. Chemistry

BL4U

Chemical State Mapping of a Heterostructured Oxygen Catalyst using
STXM
J. Wang, J. Chung and J. Lim

Department of Chemistry, College of Science, Seoul National University, Seoul, 08826, Republic of Korea

Ⅲ-3

oxyhydroxide. This deduction was also supported byvarious other techniques including in-situ XAFS,
online ICP-MS, post-mortem TEM, etc. Without
forming the heterointerface, the surface of pristine
LiCoO2 was transformed into spinel LiCo2O4,
resulting in an inferior OER activity. This work
highlighted the role of heterointerface in modulating
the dynamic structural reconstruction of catalysts
during water electrolysis. The corresponding
manuscript is under draft now and will be submittedsoon.

Water electrolysis is regarded as one of the mostpromising methods for clean hydrogen production [1],where the sluggish kinetics of oxygen evolution
reaction (OER) at the anode of a water electrolyzer
compromised the energy efficiency [2]. For the
purpose of boosting the OER rate, we proposed a newheterostructured OER catalyst by mating MoS2
dichalcogenide with layered LiCoO2 oxide. The asprepared hybrid catalyst (MML) outperformed thecommercial RuO2 in catalyzing the OER anddemonstrated remarkable stability. However, it is wellknown that both MoS2 and LiCoO2 are inert in OER
activity. In order to look into the mechanism behindthe synergistic performance enhancement, we appliedscanning transmission X-ray microscopy (STXM)
with several in-situ/ex-situ techniques to probe thedynamic structural change and to clarify the actual
active species of the catalyst during the reaction.
The chemical state of MML sample before and after
the OER was mapped around the Co L-edge and Mo
M-edge at the BL4U beamline of the UVSOR.
Hybridization with MoS2 was found to lower the Co
valence state of LiCoO2, as clearly visualized from themapping in Fig. 1 and supported by the representativeline-cut spectra showing the negative shift of the Co
L-edge spectrum of MML relative to that of pristine
LiCoO2. In addition, the homogenous distribution of
Co valence states within the MML particle suggested
the thorough mixing of the MoS2 and LiCoO2
components, which is expected to be beneficial tomaximize the heterointerface density and tune theelectronic structure. The maintenance of Mo in MML
is confirmed by the Mo M-edge spectrum. However, it
is challenging to judge the Mo valence state change
from this soft XAS spectrum. To supplement this Mo
data, XAFS around the K-edge was scanned, which
demonstrated the reduced Mo in MML. From theoxygen K-edge spectrum, the hybridization of MoS2
with LiCoO2 led to the formation of oxidized oxygenmoieties, which can be explained by the coordinationof Co with S after the hybridization. Replacement ofoxygen with less electronegative ligands (i.e., S)
potentially activated the oxygen redox.
The MML sample after the catalysis was also
investigated. From the valence state mapping, Co wasoxidized during the OER, leading to a higher valence
state. The oxidized Co in LiCoO2 was accompanied by
the leaching of Li, which process led to the structural
reconstruction of LiCoO2 forming the cobalt

Fig. 1. Chemical state mapping around the Co L-edgeof MML particle before and after the OER. A LiCoO2
particle is also provided as a reference. The
representative line-cut spectra of the MML sample
around the Co L-edge, O K-edge, and Mo M-edge areshown below.

[1] Wang J, Gao Y, Kong H, Kim J, Choi S, Ciucci F,
Hao Y, Yang S, Shao Z, Lim J. Chem. Soc. Rev. 49(2020) 9154.
[2] Wang J, Kim SJ, Liu J, Gao Y, Choi S, Han J, Shin
H, Jo S, Kim J, Ciucci F, Kim H, Li Q, Yang W, Long
X, Yang S, Cho S, Chae K. H, Kim M. G, Kim H, Lim
J. Nat. Catal. (2021) https://doi.org/10.1038/s41929021-00578-1.

102

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Ⅲ -3. Chemistry

BL4B

Detection Efficiency of a Funnel MCP Estimated for Its Use in a Magnetic
Bottle Electron Spectrometer
Y. Hikosaka

Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
Magnetic bottle electron spectrometer, utilizing an
inhomogeneous magnetic field to capture electrons
formed by photoionization, is a very efficient electron
spectroscopic tool and enabling one to perform
multielectron
coincidence
spectroscopy
very
effectively. The electrons captured over 4π-steradiansolid angle are guided to a detector (usually amicrochannel plate (MCP) detector) ending a longflight path. Ions formed together with electrons can bedetected with the same detector, by applying a pulsed
electric field to the photoionization region [1-3]. The
ion detection capability thus added to a magnetic bottle
electron spectrometer leads to efficient coincidence
measurements of multi-electrons and ions. The
coincidence efficiency for the multiple particles is the
product of the detection efficiencies for individual
particles. Thus, gaining higher detection efficiency foreach particle is crucial in achieving more effective
coincidence measurements.
A standard MCP detector of 32-mm active diameterand 60% open area ratio had been employed in ourprevious multielectron-ion coincidence measurements[3]. For the electron detection, the coincidence
efficiency limited by the detection efficiency of the
MCP was practically observed [3,4]. In this work, wehave newly introduced an MCP detector (40-mm
active diameter) consisting of funnel micropores,
instead of the previous one. The MCP has a large open
area ratio (90%), and high detection efficiencies forelectrons and ions are expected.
The detection efficiency of the funnel MCP for
detections of electrons and ions was estimated on its
use in the magnetic bottle electron spectrometer. A
single mesh of 88% transmission was placed in frontof the MCP, to avoid a leak of the electric potential of
the MCP front. The electron detection efficiency,
estimated from the number of Auger electrons from Ar
2p core-hole measured in coincidence with therelevant 2p photoelectron, is presented in Fig. 1 as afunction of kinetic energy. The electron detection
efficiency, observed to be constant around 0.7, is quitefavorable, though it does not reach the open area ratioof the funnel MCP. The detection efficiency for ions,plotted in Fig. 2, was determined from the numbers ofelectrons ejected in known ionization paths incoincidence with the formed Xe ion. While thedetection efficiency for the singly charged Xe ion is
not very favorable on the present extraction pulse (2kV height), those for highly-charged Xe ions are close
to the value reflecting the open area ratio of the MCP.
The present study proves that the use of the funnel

MCP is promising in achieving more efficient
multielectron-ion coincidence measurements.

Ⅲ-3

Fig. 1. Electron detection efficiency of the funnel
MCP estimated as a function of kinetic energy.

Fig. 2. Detection efficiency of the funnel MCP for Xe
ions.

[1] A. Matsuda, M. Fushitani, C.-M. Tseng, Y.
Hikosaka, J.H.D. Eland, and A.Hishikawa, Rev. Sci.
Instrum. 82 (2011) 103105.
[2]J.H.D. Eland, P. Linusson, M. Mucke, and R. Feifel,
Chem. Phys. Lett. 548 (2012) 90.
[3] Y. Hikosaka and E. Shigemasa, Int. J. Mass Spectrom.
439 (2019) 13.
[4] Y. Hikosaka, M. Sawa, K. Soejima, and E. Shigemasa,
J. Electron Spectrosc. Relat. Phenom. 192 (2014) 69.

103

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