Ⅲ-3
Chemistry
ChemistryBL3UⅢ -3. Chemistry

BL3U

Solvent-Induced Transition of Polymorphological Chiral SupermolecularArchitectures in Bent-Core Liquid Crystal Dimer/Nematic Binary Mixtures
as Studied by Resonant Soft X-ray Scattering (RSoXS) at UVSOR
F. Araoka1, Y. Takanishi2, K. V. Le3 and H. Iwayama4,5

RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan
2
Faculty of Science, Kyoto University, Kyoto 606-8502, Japan
3
Faculty of Science, Tokyo University of Science, Tokyo 162-8601, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
5
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan1

Nano-scaled chiral superstructures, such as tilted
lamellar (smectic) structures or helical nanofilaments(HNFs), are often observed in polar (or apolar) softmesophases of achiral bent-core molecules, although
their chemical structure has no chiral carbon. The socalled B4 phase is one of such soft-mesophases, inwhich chirality is macroscopically recognizable as
millimeter-sized domains optically segregated under apolarizing microscope. There are two types of B4
domains resembling each other, originated from two
different nanoscopic structures; One is filled withbundles of polar HNFs with a pitch of several tens tohundreds nm, and the other is the so-called dark
conglomerate (DC) in which concentric polar lamellar
structures are interconnected to form bicontinuous
pores like a sponge. However, in both cases, the polartilted lamellar structure is essential and thus almost
identical diffraction patterns are obtained byconventional small angle X-ray scattering (SAXS).
Recently, we discovered that these two structures areinterchangeable by adding a nematic solvent (ZLI-2293,
Merck) to the host bent-core molecule (12OAz5AzO12).
Besides, further addition of the nematic solvent induced
an unprecedented nano-tubular structure like a “macaroni”
as a novel chiral state. This nanoscopic morphologicalchange was first confirmed with scanning electron
microscopy (SEM, Fig. 1) – the result suggests thatphase separation reduces interfacial free energy andcreates spaces to allow the lamellar to be more twisted,leading to the structural transition from DC to macaroni
via HNF. However, the SEM technique requires vacuum
for electrons to fly, and thus the samples were fractured
to expose the internal structure and washed with Hexane
to completely remove the solvent nematic molecule.
This leaves uncertainty if the bulk structures are surely
preserved during the fracturing/washing process or not.
Meanwhile, HNF/DC are just morphologicallycharacterized, and hence electron density is basicallynot spatially modulated by these structures. This meansthat usual X-ray diffraction/scattering is not very useful
to investigate the present system. For these reasons, we
performed resonant soft X-ray scattering (RSoXS)
measurements using X-ray whose energy is close to thecarbon K-edge absorption, which allows us to analyze
the nanoscopic structural change in such amorphologically transformable system.

Our RSoXS setup was prepared in BL3U of UVSOR
at IMS – A homemade vacuum chamber equipped with acooled CCD camera (Newton, Andor) was newly
designed for small angle detection (2θ~1-15°). In thepresent study, the X-ray photon energy was chosen as
284.5 eV, corresponding to the carbon K-edge absorptionof the present sample mixtures.
RSoXS patterns for HNF, DC and Macaroni arecompared in Fig. 2, which clearly shows transitions dueto the morphological change among these states. HNFs,
appearing in the middle doping range, show relatively
sharp scattering patterns at the scattering angle
corresponding to the half-pitch periodicity of the twisting
filaments. On the other hand, DCs show broad peaks at
the slightly smaller scattering angle region than HNFs,
which would be corresponding to the average distances
between the lamellar inter-connections. Interestingly,
the macaroni state shows just scarce signals in thisregion, meaning almost no nanoscopic structural
periodicity. Needless to say, these confirm that thepresent RSoXS setup works well for structuralinvestigation for such soft-mesophases.

Fig. 1. Nanoscopic morphological transformation
among DC, HNF, and macaroni as observed by SEM.

Fig. 2. RSoXS pattern alteration corresponding to thenanoscopic morphological transformation.

105 1 Ⅲ03-

Ⅲ-3

BL1U
Ⅲ -3. Chemistry

BL1U

Energy-Dependence of Photoelectron Circular Dichroism of Chiral Molecules
H. Kohguchi1, Y. Hikosaka2, T Kaneyasu3, S. Wada1, H. Ohta4, 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

Ⅲ-3

A simple explanation of the manifestation ofphotoelectron circular dichroism (PECD), which ismeasured as forward-backward asymmetry of thephotoelectron angular distribution with circularly
polarized light, can be that the outgoing photoelectron
is affected by a chiral potential originated from thechiral core ion. The intuitive model indicates that theslower photoelectron can exhibit the larger PECD.
Actually, most of the PECD measurements so far
carried out for various chiral molecules demonstrated
decreasing PECD parameters (b1) as the higher photon
energies. However, the b1 parameters of the individual
electronic states varied in an independent manner,
showing the state-specificity. The energy-dependence
and state-dependence of PECD are not simply
understood with a simple model but should be
examined based on the precise measurements andaccurate theoretical calculations, both of which canprovide novel pictures for the PECD mechanism.
We have conducted the PECD measurements for S
methyl oxirane and other chiral molecules with
employment of circular polarized light at BL1U atvaried photon energies [1]. Methyl oxirane (propyleneoxide) is a typical chiral molecule, whose PECD has
been intensively studied. Our results are shown in Fig.
1, where the photon energy-dependence is shown in aseries of the image data for (a) 10.3 eV, (b) 11.0 eV, (c)12.0 eV, (d) 12.7 eV, (e) 13.3 eV, and (f) photoelectron
kinetic energy (PKE) scale. Distinct ring structures
corresponding to individual electronic states appearedat the higher photon energy than (a) 10.3 eV (close to
the ionization threshold) with particular PECD, whose
positive and negative b1 values are represented by red
and blue colors. The b1 value of each ring decreases as
the elevated photon energy, but the decreasing
behaviors were not monotonic but rather dependent on
the states. The strongest PECD observed in the 2 eV
PKE region at (c) hν = 12.0 eV rapidly disappeared at
an only slightly larger photon energy of (d) hν = 12.7
eV, while other bands kept the contrast of the blue/redcolor (b1 PECD parameter) for the wider photon
energy variations.
The present results are qualitatively similar to theprevious study of methyl oxirane [2]: the sign of the b1
parameters of the three electronic states were well
reproduced. We extended our measurements for thefiner intervals of the photon energy to examine theenergy-dependence of PECD. A faint feature of thesign change of PECD with the varied photon energy
was found in the second band, which is more visible in
the polar representation of the observed results (Fig. 1.
lower). These results will be verified in comparison
with theoretical calculations.
Raw Images of PECD

Polar Plot Images of PECD

Fig. 1. (Upper) Difference images of photoelectron
scattering with left-hand and right-hand circularly
polarizations and (Lower) the polar plot presentationsof PECD of S-methyl oxirane at varied photon
energies.
[1] H. Kohguchi, Y. Hikosaka, T Kaneyasu, S. Wadaand Y-I. Suzuki, UVSOR Activity Report 2019 47(2020) 107.
[2] G. A. Garcia, H. Dossmann, L. Nahon, S. Daly and
I. Powis, Phys. Chem. Chem. Phys. 16 (2014) 16214.

106 2 Ⅲ03-

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Ⅲ -3. Chemistry

BL1U

Photoionization of Atoms by Double-pulsed Radiation from a TandemUndulator
T. Kaneyasu1, Y. Hikosaka2, S. Wada3, M. Fujimoto4,5, H. Ota4, H. Iwayama4,5and M. Katoh6,4

1
SAGA Light Source, Tosu 841-0005, Japan
Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
3
Graduate School of Advanced Science and Engineering, Hiroshima University,
Higashi-Hiroshima 739-8526, Japan
4
Institute for Molecular Science, Okazaki 444-8585, Japan
5
The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
6
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan
2

Recently, we have shown a new ability of a tandemundulator in a synchrotron to perform wave packet
interferometry using double-pulsed light wave packets.
This has enabled the quantum manipulation of theatomic system, so-called coherent control, by synchrotron
radiation. The potential of this method has been
demonstrated in the proof-of-principle experiments on
gas-phase atoms [1-3]. In these experiments, we used adouble-pulsed light wave packet to produce a pair ofelectron wave packets (superposition of eigenstates) thatinterfere in the single atom. The quantum phasedifference between the interfering electron wave packets
determines the behavior of the quantum state to becontrolled or probed, and is precisely controlled byvarying the time delay between the double-pulsed
components of light wave packet in the attosecond level.
Here, we extend this approach to the electron wave
packets produced in an ionization continuum. The
experiment was carried out at the undulator beamline
BL1U. The double-pulsed light wave packet was
generated by a tandem-undulator in the synchrotron
ring. The waveform of the light wave packet wascharacterized by time-separated 10-cycle oscillations.
The fundamental radiation wavelength was set to ~40
nm. The double-pulsed light wave packet interactedwith a helium atom, leading to the production of a pairof photoelectron wave packets that interfere in freespace. To verify the interference between the photoelectron
wave packets, we measured a photoelectron spectrum
using a hemispherical electron analyzer fixed at anangle of 55° with respect to the polarization axis.
Figure 1 compares the photoelectron spectra measured
for the radiation from a single undulator (a and b) andtandem-undulator (c and d) configuration. The
photoelectron spectra in a and b show single peaked
distributions centered at around 5 eV. This spectral
shape simply reflects the spectral distribution of theradiation from the single undulator which is characterized
by a Gaussian-like distribution with 10 % width of thecentral photon energy. In contrast, the photoelectron
spectra show clear interference patterns when thetandem undulator is used to ionize the helium atoms.
Moreover, the spacing between interfering fringes

depends on the time separation between the doublepulsed components of the light wave packet. To interpretthe experimentally measured data, we have calculated
the photoelectron spectrum (not shown here), and agood agreement between the experimental andcalculation results is obtained. Therefore, it is reasonable
to conclude that we observed the interference between
the photoelectron wave packets in the present study.

Fig. 1. Photoelectron spectra of helium atoms measured
by using radiation from (a) upstream undulator, (b)downstream undulator, (c) and (d) tandem undulator.
The time delays between the double-pulsed componentsof light wave packet are (c) 2 fs and (d) 4.5 fs.

[1] Y. Hikosaka et al., Nat. Commun. 10 (2019) 4988;
ibid. 12 (2021) 3782.
[2] T. Kaneyasu et al., Phys. Rev. Lett. 123 (2019)
233401.
[3] T. Kaneyasu et al., Phys. Rev. Lett. 126 (2021)
113202.

107 3 Ⅲ03-

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BL2B
Ⅲ -3. Chemistry

BL2B

Electronic State Changes of Cu Nanoparticles on Rutile TiO2(110) by
CO Exposure
1

Ⅲ-3

K. Mitsuhara1, K. Ide2, H. Takatani2, Y. Hasegawa2 and M. Takizawa2

Ritsumeikan Global Innovation Research Organization, Ritsumeikan University, Kusatsu 525-8577, Japan2
Department of Physical Science, Faculty of Science and Engineering, Ritsumeikan University,
Kusatsu 525-8577, JapanFor Cu based catalysts, it exhibits strong catalytic
activities for the carbon monoxide oxidation, water-gas
shift reaction, methanol oxidation and others [1].
However, their performance is not fully understood. In
previous study, we have found the growth mode of Cu
nanoparticles deposited on the rutile TiO2(110) surfaces
by medium energy ion scattering (MEIS) [2]. As a result,
the two-dimensional (2D) islands grow initially up to Cu
coverage of ~0.5 ML and then the three-dimensional(3D) island-growth becomes dominant. The electronic
state of supported metal particles is also known to playa critical role in determining catalytic activity.
Understanding the adsorbate-induced changes in thesurface electronic state is therefore important. In thisstudy, we manifest the reaction of Cu nanoparticles
supported rutile TiO2(110) with carbon monoxide byphotoelectron and photon-induced secondary electrons
emission spectroscopy.
The experiment was performed at beamline BL2B of
the UVSOR synchrotron factory at the Institute for
Molecular Science. We prepared the oxygen-rich rutileTiO2(110) surfaces (O-TiO2) by exposure of O2 (5 N)
onto the reduced surfaces (R-TiO2), which were formedby sputtering with 0.75 keV Ar+ followed by annealing
at 870 K for 10 min in UHV. Cu was deposited on theclean surfaces at RT with a Knudsen cell at a rate of 0.08
ML/min under UHV condition. Here, 1 ML means
1.77×1015 atoms/cm2, corresponding to the areal densityof Cu(111).
Figure 1 (a) shows secondary electron spectra taken forCu(0.2 ML)/O-TiO2(110) and oxidized Cu(0.2 ML)/OTiO2(110) before and after CO exposure, respectively.
After O2 exposure of 500 L, the work function increases.
This electronic state changes indicate an upward band
bending. The mechanism of this upward band bending
may be considered as follows: Cu nanoparticles areoxidized to Cu2O by oxygen exposure and then the
upward band bending is caused by a p-n junction
between Cu2O and TiO2 substrate. After CO exposure of
15,000 L, the work function slightly decreased, whilethe valence band spectra and Ti 3p and O 2s lines did
not change nor shift significantly (not shown). Thechange in work function showed the same tendency
even for Cu coverage of 1.0 ML [see Fig.1 (b)]. The
work function of TiO2(110) surfaces scatter largely
owing to strong dependence upon bulk and surface
defect densities. Note that work function consists ofbulk and surface dipole terms and the surface term
originates from a surface dipole consisting of positive

cores and valence electrons near a surface. Therefore, thisresult is ascribed to elimination of the electronegative
adsorbate oxygen on top of the surface resulting in
weakening the surface dipole with a negative polarity on
the vacuum side. These results may suggest that
presence of Cu nanoparticles on O-TiO2(110) strongly
enhances the reaction between O and CO.
(a)

(b)

Fig. 1 Secondary electron spectra taken for (a) Cu(0.2ML)/O-TiO2(110) and (b) Cu(1.0 ML)/O-TiO2(110)before and after CO expos[1] J. M. Thomas et al., Principles and Practice ofHeterogeneous Catalysis, VCH, New York, 1997.
[2] T. Aoki et al., e-J. Surf. Sci. Nanotechnol. 16 (2018)225.

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Ⅲ -3. Chemistry

BL3U

X-ray Absorption Spectra of Aqueous Cellobiose
T. Sasaki and D. Akazawa

Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, The University of Tokyo,
Kashiwa 277-8561, Japan
Biomass conversion using water or an ionic liquid asa solvent without using an organic solvent is an
important research topic. There have been many studies
on biomass-related compounds in solution, but there are
few reports on their molecular theory. We have studied
the conversion process by dehydration reaction ofpolyalcohol as models of sugar molecules and foundthat the solvation structure with water molecules and theinteraction with protons are important 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 from cellobiose
to glucose, that is typical of biomass-derived sugar
alcohol conversion 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.
XAS measurements for liquid samples wereconducted at UVSOR BL3U using facilities developed
by Nagasaka et al. [3]. 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.
Figure 1 shows C-K edge XAS spectra for cellobiose
aqueous solutions with concentrations specified in the
figure. Fig. 2 shows O-K edge XAS spectra for cellobiose
aqueous solutions as well as the spectrum for water (0M). Molecular dynamics calculations for the solutions
and the XAS simulations were conducted using CP2K
program to interpret the XAS spectra.
In Fig. 1 three peaks were observed at 289.3, 290.7
and 293.6 eV, named as “A”, “B”, and “C”, respectively.
A peak at 290.0 eV was defined as “A”, which does notappear for the aqueous solution but is expected to appear
in the gaseous isolated cellobiose molecule as found by
MD and XAS simulation. With the XAS simulation it
was concluded that A, B and C correspond to theabsorption by carbon atoms of the alcohol group, thehemiacetal group and the both of these groups,
respectively. Temperature and concentration dependences
of XAS spectra for cellobise aqueous solutions were
measured and relative intensity change of three peaks
were observed, which can be explained by the change in
the number of hydrogen bond between cellobiose andwater. These results were published recently [4]. The
analysis of O-K XAS spectra for cellobiose aqueous
solutions is under way.

Ⅲ-3
Fig. 1. C-K XAS spectra for cellobiose aqueous
solutions at 25 °C. Blue : 0.20 M, Green : 0.15 M.

Fig. 2. O-K XAS spectra for cellobiose aqueous
solutions at 25°C. Blue : 0 M, Purple : 0.20 M, Green :0.05 M.

[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] M. Nagasaka et al., J. Electrosc. Relat. Phenom. 200(2015) 293.
[4] D. Akazawa et al., J. Chem. Phys. 156 (2022) 044202.

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BL3U

X-ray Absorption Spectroscopy Study of 4-MBA on Gold Surfaces
1

Ⅲ-3

I. Sakaida1, S. Ohno1, M. Nagasaka2

Graduate School of Engineering Science, Yokohama National University, Yokohama 240-8501, Japan
2
Institute for Molecular Science, Okazaki 444-8585, Japan

It is important to understand the behavior of
biomolecules on solid surfaces for the application to
medical device, biosensor and biocompatible material.
It is essential to study the adsorption and desorption
behavior of molecules and their response to the appliedfields. It is of particular importance to analyze thedynamic behavior of biomolecules on surface inelectrolyte solutions close to the realistic condition in
the body of living creatures [1,2]. However, the numberof studies appears to be still quite limited, especially forthe investigation of the dependence of the molecularorientation and ionization on the electrolyte solutions.
In this study, potential-dependent adsorption/desorption
behavior of 4-mercaptobenzoic acid (4-MBA) on Au(111)and Au membrane surfaces have been investigatedusing soft X-ray absorption spectroscopy (XAS) in the
fluorescence yield mode for the former case, and in thetransmission mode in the latter case. The experiments
were performed on the soft X-ray undulator beam line at
UVSOR-III, BL3U. We used NaClO4 as the electrolyte
solution. For the adsorption of 4-MBA molecules, thesamples were immersed in 1mM 4-MBA/ethanol
solution for more than 30 min.
In our previous study, we have studied theadsorption/desorption behavior of 4-MBA on Au films
using surface differential reflectance spectroscopy(SDRS) combined with cyclic voltammetry (CV) [3].
The key issue was the interaction between functionalgroup (-COOH) and Au films through Coulombinteraction depending on the applied biases and pH
conditions. Redox processes involving charge transfer
were clearly observed CV and the relation between thechange in the reflectance spectra were investigated indetail. Interestingly, we found some precursor
phenomena to cause significant changes in thereflectance spectra with no corresponding signal in thecyclic voltammogram. This indicates that the suchchanges in the reflectance spectra are not related to thecharge-transfer-type reactions but rather to the subtle
change in the orientation/conformation of 4-MBA
molecules.
To our knowledge, there has been no serious effort tostudy the 4-MBA/Au system using XAS. We, therefore,
tried to investigate the possible precursor phenomena
addressed above. Firstly, we have tried to observe theeffects on Au(111). However, we could not obtain theclear data showing the adsorption/desorption behaviorof 4-MBA. This could be understood because of therelatively low signal-to-noise ratio in the fluorescence
yield mode, and the amount of the adsorbed 4-MBA
might be less than the detection limit. In order toimprove the surface sensitivity, we next tried to observe

the effects on membrane Au surface.
Our preliminary results showed clear spectralfeatures in the O K-edge region, as shown in Fig. 1.
One is due to the π* component assigned to the C=O
double bond, and the other is possibly due to theformation of the hydrogen bond. The investigation of
the C K-edge region is underway.
The next step should be the observation of the slighteffects due to the change in the orientation/conformation
depending on the applied bias to the electrode (Aumembrane). Obviously, we have to conduct the surfacesensitive measurements further to elucidate such subtle
effects.
It should be noted that more distinct change in the
XAS spectra can be envisioned in the case of cysteine
molecules, for which two of them can attach to form acystine molecule [3]. At this point, we have establishedthe measurement set up for the transmission mode.
Therefore, we now also plan to re-investigate thereactions of biomolecules, in terms of the ionization of
the functional groups (-COOH, -NH3).

Fig. 1. O K-edge XAS spectrum for 4-MB.

[1] R. LeParc et al., Langmuir 22 (2006) 3413.
[2] C. I. Smith et al., J. Electrochem. Soc. 150 (2003) 1.
[3] N. Ikeda et al., ALC’19, AP-52 (2019) 22.

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BL3U

Resonant Soft X-ray Scattering Equipment Evaluated by Chicken Leg’s
Collagens and 100-nm Silica Nanoparticles
H. Iwayama1,2, F. Araoka3 and Y. Takanishi4

UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
3
RIKEN Center for Emergent Matter Science, Wako 351-0198, Japan
4
Faculty of Science, Kyoto University, Kyoto 606-8502, Japan
1

2

Resonant Soft X-ray Scattering (RSoXS) is similar to
Small Angle X-ray Scattering (SAXS) and can provide
information on the mesoscopic structure (1 ~ 100 nm) of
samples. Due to the resonance process, RSoXS haveselectivities of elements, functional groups and molecularorientations. In particular, since soft x-ray region include
K-edge energies of light element such as carbon, nitrogenand oxygen, RSoXS will be a powerful tool to investigate
soft matter, which mainly consists on light element atoms.
In 2020, we started to develop RSoXS equipments andsucceeded in characterizing liquid-crystal materials. To
improve an accuracy of our RSoXS equipments, wemeasured chicken collagen and silica nanoparticles asstandard substances.
Our RSoXS measurements were performed at
UVSOR BL3U. Figure 1 shows a schematic draw of anexperimental setup. Samples of chicken leg’s collagenand 100nm-silica nanoparticle were fixed on Si3N4
membranes. The photon energy is 284 eV. Scattering
light were detected by soft x-ray camera (Andor
BN940P). This RSoXS equipment covers scattering
angles, 2θ, ranging from 0 to 15°.
Figure 2(a) shows a scattering image of the chicken
leg’s collagens. We find three weak ring structures.
From the image, we obtained a scattering intensity as
a function of scattering vector, q, which are shown in
Fig. 2(b). Three peaks at q = 0.105, 0.212, 0.320 nm-1
indicates that the sample of the chicken collagen haveperiodic structure of 59.3 nm, which is slightly different
from the reference value of 63.8 nm.
Figure 3(a) shows a scattering image of 100-nm(diameter) silica nanoparticles. We find striped ring
structures. From the image, we also obtained a scattering
intensity as a function of scattering vector, q. As shownin Fig. 3(b), we find oscillation structures. By using
theoretical equation of a scattering intensity forspherical sample, we fitted experimental curves withthose of the 110-nm nanoparticle.
Thus experimental results are slightly different from
actual values, suggesting that we need the standard
sample for calibrations of our RSoXS equipment.

Fig. 1. Schematic view of our RSoXS equipment.

Ⅲ-3

Fig. 2 (a) Scattering image of chicken leg’s collagens.
The color scale is a log scale. (b) Scattering intensity
as a function of scattering vector, q.

Fig. 3 (a) Scattering image of 100-nm silica nanoparticles.
The color scale is a log scale. (b) Scattering intensity
as a function of scattering vector, q. Red and blue lines
are experimental and theoretical one, respectively.

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BL3U

Oxygen K-edge X-ray Absorption Spectroscopy of Aqueous Dimethyl
Sulfoxide Solutions at Different Concentrations
M. Nagasaka1, 2Institute for Molecular Science, Okazaki 444-8585, JapanThe Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
1

2

Ⅲ-3

Dimethyl sulfoxide (DMSO) is a widely usedcosolvent, and aqueous DMSO solutions show
numerous physical properties that show maxima or
minima in the middle concentration region [1]. Several
studies determined microscopic structures of aqueous
DMSO solutions, where hydrogen bond (HB) structuresof S=O groups in DMSO with water are formed and arechanged at different molar fractions [2]. However, themechanism of the HB formation of DMSO with water
have not fully understood. In this study, we have studied
the concentration dependence of the HB structures of
DMSO with water in aqueous solutions by using O Kedge X-ray absorption spectroscopy (XAS).
The experiments were performed at soft X-ray
beamline BL3U. O K-edge XAS of aqueous DMSO
solutions were measured by using a transmission-type
liquid flow cell [3]. Liquid samples are exchanged bya tubing pump without changing the beam positions.
Figure 1 shows O K-edge XAS spectra of aqueous
DMSO solutions (DMSO)x(H2O)1−x at different
concentrations at 25 °C. In O K-edge XAS of neat water(x = 0.0), the pre-edge peak at 535 eV is assigned as
the transition of O 1s electron to the 4a1 unoccupied
orbital in water and reflects HB structures amongwater molecules, as observed in O K-edge XAS ofliquid water at different temperatures [4]. On the other
hand, the peak at 532 eV corresponds to the transitionof O 1s electron to the S=O π* orbital in DMSO [5].
From the fitting procedures, we have determined theenergy shifts of the pre-edge peaks in water and thefirst peaks of S=O π* orbitals in DMSO at the different
molar fractions of DMSO.
Figure 2 shows the energy shifts of the first peaks of
DMSO S=O π* orbitals from that of neat DMSO (x =1.0). By increasing the molar fraction of water (1 – x),
the S=O π* peaks show the higher energy shifts, whichshows two concentration regions with the border of x
= 0.4. In the DMSO-rich region (0.4 < x < 1.0), theslope of the energy shift is 164 meV / (1 – x). In thewater-rich region (0.05 < x < 0.4), on the other hand,
the higher energy shift of the S=O π* peak isaccelerated (271 meV / (1 – x)). The pre-edge peaks inwater also show characteristic concentration dependence,
which shows three concentration regions with theborders of x = 0.2 and x = 0.6. For revealing theconcentration dependence of the energy shifts in O Kedge XAS, we will perform molecular dynamics
simulations and inner-shell quantum chemical
calculations of aqueous DMSO solutions.

Fig. 1. O K-edge XAS spectra of aqueous DMSO
solutions at different concentrations.

Fig. 2. Energy shifts of the first peaks of DMSO S=O
π* orbitals from that of neat DMSO (x = 1.0) as afunction of molar fraction of DMSO.

[1] S. Roy and B. Bagchi, J. Chem. Phys. 139 (2013)
034308.
[2] K.-I. Oh et al., Angew. Chem. Int. Ed. 56 (2017)11375.
[3] M. Nagasaka and N. Kosugi, Chem. Lett. 50 (2021)
956.
[4] M. Nagasaka et al., J. Phys. Chem. B 121 (2017)10957.
[5] L. I. Vogt et al., RSC Adv. 10 (2020) 26229.

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BL3U

Carbon K-edge X-ray Absorption Spectroscopy of Aqueous Ethanol
Solutions at Different Concentrations
M. Nagasaka1,2, M. Bouvier1, H. Yuzawa1 and N. Kosugi1,2

Institute for Molecular Science, Okazaki 444-8585, JapanThe Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
1

2

Aqueous ethanol (EtOH) solutions show anomaliesof thermodynamic and transport properties [1]. These
anomalies would be occurred by the intermolecularinteractions between EtOH and water (H2O). In theprevious studies, it is suggested that the EtOH-H2O
mixed clusters are formed in the middle concentration
region [2] and the hydrophobic hydration of EtOH isformed in the low concentration region [3]. In thisstudy, we have investigated the local structures aroundthe ethyl group in EtOH by using carbon K-edge X-ray
absorption spectroscopy (XAS) of aqueous EtOH
solutions at different concentrations.
The experiments were performed at soft X-ray
beamline BL3U. C K-edge XAS of aqueous EtOH
solutions were measured by using a transmission-type
liquid flow cell [4]. Liquid samples are exchanged bya tubing pump without changing the beam positions.
Figure 1(a) shows C K-edge XAS spectra ofaqueous EtOH solutions at different concentrations at
25 °C. Each spectrum is fitted by four peaks, where
peak A is the lowest peak around 287.3 eV. Figure 1(b)shows the energy shifts of peak A relative to that ofliquid EtOH (x = 1.0) as a function of the molar
fraction of EtOH (x). We have found that the energy
shift of peak A shows four concentration regions (I, II,
III, and IV). In the region I (1.0 > x > 0.8), peak A
shows the lower energy shift by increasing the molar
fraction of H2O. In the region II (0.8 > x > 0.25), peak
A shows the slightly higher energy shift by increasing
the molar fraction of H2O. The lower energy shift ofpeak A is observed in the region III (0.25 > x > 0.15)
and is accelerated by increasing the molar fraction of
H2O in the region IV (0.15 > x > 0.05).
From the inner-shell quantum calculations, we haveinvestigated the molecular interaction between EtOH
and H2O at the four concentration regions. In the region
I, the hydrogen bond (HB) structure of EtOH – EtOH issimply substituted to that of EtOH – H2O. In the region
II, the EtOH clusters are formed by the hydrophobic
interactions of the ethyl group in EtOH, resulting in theenhancement of the HB structure of H2O – H2O as
observed by O K-edge XAS [5]. Whereas a phasetransition like behavior is observed in aqueous methanol
solutions [6], there is no phase-transition like behavior
in aqueous EtOH solutions due to the stronghydrophobic interactions in EtOH. In the regions III andIV, the size of EtOH clusters becomes smaller, resulting
in the increase of the hydrophobic hydration of EtOH in
the HB network of H2O.

Ⅲ-3

Fig. 1. (a) C K-edge XAS spectra of aqueous EtOH
solutions at different concentrations. (b) Energy shiftsof peak A relative to that of liquid EtOH (x = 1.0) as afunction of molar fraction of EtOH (x).

[1] F. Franks and D. J. G. Ives, Q. Rev. Chem. Soc. 20(1966) 1.
[2]K. Nishikawa et al., J. Phys. Chem. 97 (1993) 10824.
[3] H. S. Frank and M. W. Evans, J. Chem. Phys. 13(1945) 507.
[4] M. Nagasaka and N. Kosugi, Chem. Lett. 50 (2021)
956.
[5] M. Nagasaka et al., UVSOR Activity Report 201947 (2020) 114.
[6]M. Nagasaka et al., J. Phys. Chem. B 118 (2014) 4388.

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The C–Si Bond Length of Organosilicon Compounds in Organic Solvent
Probed by Carbon K-edge X-ray Absorption Spectroscopy
S. Okumura1,2, M. Nagasaka1,2, H. Takaya1,3, and Y. Uozumi1,2

Institute for Molecular Science, Okazaki 444-8585, JapanThe Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
3
Institute for Chemical Research, Kyoto University, Uji 611-0011, Japan
1

2

Ⅲ-3

Although the reactivity of organic compounds isclosely related to the bond length at the reactive site, it
is difficult to know the bond length in organic solvents
experimentally. Soft X-ray absorption spectroscopy(XAS) has a potential to determine the chemical bondsince soft X-ray XAS observes electronic structures oflight elements such as C, N, O, etc. Recently, we havedeveloped liquid flow cells for XAS in transmission
mode [1]. Hydration of cyanopyrazine on titaniumoxide catalysts has been studied by C K-edge XAS, but
this study only observed the reaction kinetics [2]. It is
still difficult to reveal the relation of the bond length at
the reactive site with the reactivity by soft X-ray XAS.
In this study, we have investigated the C–Si bondlengths of the organosilicon compounds in organic
solvents, which are key compounds for the Hiyama
cross-coupling reaction [3], by using C K-edge XAS.
The experiments were performed at soft X-ray
beamline BL3U. C K-edge XAS of the organosiliconcompounds in organic solvents were measured byusing a transmission-type liquid flow cell [1]. The
liquid samples were prepared in argon filled glovebox
and were flown to the liquid cell by using a syringe
pump. Liquid temperature was set to 25 °C.
Figure 1 shows the C K-edge XAS spectra of 100 mM
trimethoxy(phenyl)silane (1) in tetrahydrofuran (THF),
ethylene glycol-derived pentacoordinate spirosilicate(2) in ethylene glycol, and fluorotrimethoxy(phenyl)
silicate (3) in THF solution. The peak around 285 eV insilane 1 is assigned as the transition from the C 1s orbitalto the C=C π* unoccupied orbital in the phenyl group.
This peak is fitted by three peaks: Peak A is thetransition from the C atom bonded with Si, peak B isthat from the ortho sites, and peak C is that from themeta sites in the phenyl group. It means that peak A
reflects the C–Si bond lengths of the organosiliconcompounds. The energy position of peak A in silane 1 is284.56 eV. The peak A in silicates 2 and 3 show lower
energy shifts by −0.02 eV and −0.06 eV from that insilane 1, respectively. We have performed the structural
optimization of these organosilicon compounds by thequantum chemical calculations and found that the C–Si
bond length becomes longer with the order of compounds
1, 2, and 3. C K-edge inner-shell calculations revealed
that the peak A shows lower energy shifts by increasing
the C–Si bond lengths. These results are consistent withthe experiments. Therefore, it is revealed that due to thelonger C–Si bond of silicate 2, it showed the higher
reactivity in the Hiyama cross-coupling reaction thanthat of silane 1. On the other hand, the reactivity ofsilicate 3 was lower than that of silane 1 despite thelongest C–Si bond length [4]. The inertness of silicate 3
would be caused by other factors such as a steric barrier,which is now investigating by the quantum calculationof the transition state in the reaction.

Fig. 1. C K-edge XAS spectra of compounds 1, 2, and3 in THF or ethylene glycol. Dashed lines show thepeak positions of silane 1 obtained by curve fitting
procedures.

[1] M. Nagasaka and N. Kosugi, Chem. Lett. 50 (2021)
956.
[2] H. Yuzawa, M. Nagasaka and N. Kosugi, J. Phys.
Chem. C 119 (2015) 7738.
[3] S. Ichii, G. Hamasaka and Y. Uozumi, Chem. Asian J.
14 (2019) 3850.
[4] C. Amatore et al., Angew. Chem. Int. Ed. 53 (2014)
6982.

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BL3U

Direct Observation of a High Valent Oxo Species of a μ-Nitrido-Bridged
Iron Phthalocyanine Dimer Deposited on a Graphite Surface
in Aqueous Solution by Soft X-ray Absorption Spectroscopy
Y. Yamada1,2 and M. Nagasaka3

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
Institute for Molecular Science, Okazaki 444-8585, Japanto the excitation of O1s – π* of Fe=O for 1oxo should
be observed at around 529 eV (Fig. 2c), whereas thepeaks for 1 having a coordinating H2O should beobserved at higher energy than 534 eV as shown in Fig.
2d (Fig. 2d). Therefore, it is considered that the peak
appeared at around 532.5 eV is assignable to theexcitation of O1s – π* of Fe=O for 1oxo. Next, we aregoing to observe the electrochemically generated 1oxoin H2O.
ONNNNFeNIII N
N
N

N

N
N
N
FeNIV N
N
N

N

N

N
N
N
N
FeNIV N
N
N

N
N
N
N
FeNIV N
N
N

H2O2

・ 0

1

Ⅲ-3

CH4

CH3OH
HCHO
HCOOH

Graphite

1oxoFig. 1. Potent methane oxidation catalyst 1 and its
reactive species 1oxo.
(a)

N

(c)

N
N
N
FeNIII N
N
N

N
N
N
N
FeNIV N
N
N

N

N
N
N
FeNIV N
N
N

N

N
N
N
FeNIV NNN

0.040

Oscillator strength

C membrane~ 20 nm

SiN membrane

・ 0

O
0.050

N

N

0.030

0.020

0.010

(b)

0.000

(d)

525

530

535

540

Photon energy / eV

OH2
N
N
N
N
FeNIII N
N
N

0.050

N

0.040

Oscillator strength

Methane is abundant in nature as natural gas ormethane hydrate. Therefore, efficient conversion of
methane into valuable raw chemicals such as methanol
is highly desired in order to use methane as a nextgeneration carbon resource. However, since highchemical stability of methane prevent its efficient C-Hbond activation, development of novel catalysts thatallow facile C-H bond dissociation of methane under
mild reaction condition is indispensable. We recently
found that a μ-nitrido-bridged iron phthalocyanine
dimer adsorbed on a graphite surface 1 (Fig. 1) efficiently
convert methane into methanol, formaldehyde, andformic acid in an acidic aqueous solution containing
H2O2 at a temperature below than 100 °C. It wasdemonstrated that 1 showed one of the most potent
methane oxidation activity among a variety ofmolecule-based catalysts and its activity was almost
comparable as that of natural particulate methane
monooxgenase (pMMO)[1]. Although it’s reactive
intermediate was confirmed to be a high valent iron-oxo
species 1oxo generated by the reaction with H2O2, theelectronic structure of 1oxo has never been investigated.
In our previous report, we confirmed that it is possible
to observe 1oxo directly by XAS under vacuum by using
a highly oriented pyrolytic graphite (HOPG) substrate
modified with the μ-nitrido-bridged iron phthalocyanine
dimer. In this study, we attempted to observe theconversion of 1 into 1oxo in an aqueous solution by using
XAS.
We first prepared a SiN membrane tip modified by
1 (Fig. 2a). A SiN membrane tip coated by 20 nm
thickness of carbon membrane was dipped in apyridine solution of the μ-nitrido-bridged ironphthalocyanine dimer. It was confirmed that the μnitrido-bridged iron phthalocyanine dimer was
successfully deposited on the carbon surface of the SiN
membrane tip by detecting the Fe L-edge XAS signals.
The SiN substrate modified with 1 was used for the
XAS measurement in an aqueous solution by using abeamline equipped with a transmission-type liquid flow
cell in BL3U of UVSOR [2]. The O K-edge XAS
spectra of 1oxo formed by the reaction with H2O2 wereobtained by using the Lambert-Beer law, ln(I0/I), where
I0 and I are the transmission signals of 1 in pure waterand 1 in a 0.5 % H2O2 aqueous solution, respectively.
It was found that the peak at around 532.5 eV wassignificantly increased after treatment with H2O2 (Fig.
2b). DFT calculation suggested that the peak assignable

Intensity / a.u.

1

N

0.030

N
N
N
FeNIV N
N
N

0.020

0.010

0.000

Photon energy / eV

525

530

535

540

Photon energy / eV

Fig. 2. (a) Structure of a SiN tip coated with 1, (b)Comparison of O K-edge XAS spectra of 1 before andafter treatment with H2O2. DFT-calculated O K-edge
XAS spectra for 1oxo (c) and 1(OH2) (d).

[1] Y. Yamada, M. Nagasaka et al., Chem Rxiv.
DOI : https://doi.org/10.26434/chemrxiv.14728860.v1.
[2] M. Nagasaka and N, Kosugi, Chem. Lett. 50 (2021)
956.

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Soft X-ray Absorption of Photocatalysts for Artificial Photosynthesis:
A Feasibility Study under Ultraviolet Light Irradiation
H. Onishi1,2, T. Hirai1, N. Ichikuni3 and T. Yoshida4

School of Science, Kobe University, Kobe 657-8501, Japan
Division of Advanced Molecular Science, Institute for Molecular Science, Okazaki 444-8585, Japan
3
Graduate School of Engineering, Chiba University, Chiba 263-8522, Japan
4
Reserch Center for Artificial Photosynthesis, Osaka City University, Osaka 558-8585, Japan
1

2

Ⅲ-3

Sodium tantalate (NaTaO3) is a semiconductor
photocatalysts which produces hydrogen–oxygen
mixed bubbles in the overall water splitting reaction,
when properly doped with metal cations [1]. We areconducting a series of studies to answer the question of
why doping with metal cations raised the quantum
yield of the reaction. Here, soft X-ray absorption isapplied for characterizing the electronic structure of
the photocatalysts in the presence and absence ofultraviolet (UV) light for bandgap excitation.
NaTaO3 particles doped with and without Sr cations
were prepared thorough a solid-state reaction. Oxygen
K-edge absorption of the particles was observed in
vacuum at room temperature with total electron yield.
Figure 1 shows the spectra of the pristine, undoped
particles.
The spectrum in the absence of UV light was wellfitted with three Gaussian functions peaked at 531.8,
532.8, and 537.2 eV (upper panel). The first andsecond peaks were assigned to electron transition fromoxygen 1s to 2p states which were covalently
hybridized with t2g states of Ta 5d orbitals. The third
peak present at a larger photon energy was assigned tothe transition to oxygen 2p states hybridized with eg
states of the Ta orbitals. NaTaO3 is a perovskitestructured compound involves TaO6 octahedra, which
provide the 5d orbitals split into t2g and eg states.
When the photocatalyst particles were irradiatedwith steady UV light produced by a 200-W Hg–Xe
lamp, absorption related to the t2g final states, the firstpeak at 531.8 eV in particular, weakened relative to thethird peak, as presented in the lower panel of Fig. 1. A
possible reason of the weakened absorption is the
conduction band partially filled with bandgap-excitedelectrons. The density of vacant states, the final statesof the K-edge absorption, should have decreased by theelectrons excited from the valence band. Covalenthybridization of the oxygen 2p and Ta 5d orbitals
would also be limited to weaken 5d-states character ofthe final states [2], since the oxidation state of Ta
cations decreased from +5 to 4+ by the bandgap
excitation.

Fig. 1. Oxygen K-edge absorption spectra of pristine
NaTaO3 photocatalyst particles observed in theabsence (upper panel) and presence (lower panel) of
UV light for bandgap excitation. The observed spectra(black curves) were fitted with Gaussian functions (redcurves). The spectra reconstructed with the functions(blue curves) are shown with residuals (thin black
curves at the top).

[1] H. Onishi, ChemSusChem 12 (2019) 1825.
[2]F. Frati, M. O. J. Y. Hunault, F. M. F. de Groot, Chem.
Rev. 120 (2020) 4056.

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Variation of the Resonance Band of Water in Soft X-Ray Absorption
Spectra of Aqueous Acetone Solutions
K. Okada1,2, C. Sugahara2, H. Iwayama3,4 and M. Nagasaka3,4

Graduate School of Advanced Science and Engineering, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
2
School of Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
3
Institute for Molecular Science, Okazaki 444-8585, Japan
4
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
1

Acetone is miscible with water in any ratio. The
binary mixture is a typical aprotic–protic solvent system[1]. A role of the acetone molecule acting as a hydrogenbond acceptor adds characteristic properties of water.
For instance, the partial molar volume of water in thismixture is 14.25 cm3/mol at 25 °C [2], which is muchless than the molar volume of water. Such specific watermolecules have a different electronic structure from thatof bulk water. The study of the electronic structure of
hydrated water is of essential importance because it
provides fundamental information on the structure of
aqueous solutions in general (e.g., [3]). In this report theO K-edge absorption spectra with various fractions ofacetone are recorded for extracting the hydrated watercomponents through an excess function: We expect that
there exists some correlation between the hydration anda deviation from Beer’s law at some photon energy.
Photoabsorption spectra of the solutions were
measured in the oxygen K-edge region on the soft Xray 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 [4]. The absorption
coefficient was evaluated so as to match the value at
547.85 eV to that tabulated in the database [5]. The
sample solutions were prepared by mixing acetone
with purified water to give 0–0.50 molar fractions ofacetone.
Distinct features are found in the absorption spectra.
Figure 1 displays some of the measured absorption
spectra of water and aqueous acetone solutions. The π*
resonance peak of acetone located at 531.13 eV for
pure liquid is now observed at 531.33 eV for thesolution with the molar fraction of acetone of 0.10. The
shift depends non-linearly on the molar fraction: Thechange is larger for a dilute region. The 4a1 resonanceband of water has a peak at 534.56 eV for pure waterand at 534.46 eV for the 1:1 molar mixture (not shownin Fig. 1). The change around the molar fraction of
0.25 is noticeable, indicating a greater change in theelectronic structure of water around this concentration.
Apparent bathochromic shift (or red shift) of the latter
resonance peak is reasonable on the basis of chemical
shift because the water molecule gets electron-rich if it
receives electrons from the carbonyl oxygen of theacetone molecule. One can safely conclude that theabsorption component of the hydrated water isembedded in the lower energy side of the band and isassigned to the resonance transition of water acting asa hydrogen-bond donor.
Further discussion requires a quantitative analysis of
the spectra. Additivity of Beer’s absorption law is valid
for non-interacting mixtures. Conversely, a deviationfrom the absorption law indicates an extent ofinteraction between the components. The deviation isexpressed as the excess absorbance. The results of theanalysis will be published elsewhere.

Ⅲ-3

Fig. 1. The O K-edge absorption spectra of liquidwater and aqueous acetone solutions measured for aseries of molar fractions of acetone.

[1] A. J. Parker, Quart. Rev. Chem. Soc. (London) 16(1962) 163.
[2] E. V. Ivanov, V. K. Abrosimov and E. Y. Lebedeva,
J. Sol. Chem. 37 (2008) 1261.
[3] S. Ohsawa, T. Tokushima and K. Okada, J. Phys.
Chem. B 125 (2021) 1881.
[4] M. Nagasaka, H. Yuzawa, T. Horigome and N.
Kosugi, J. Elec. Spectrosc. Relat. Phenom. 224 (2018) 93.
[5] C. T. Chantler et al., NIST Standard Reference
Database 66 (1995; last update in 2005), available athttps://www.nist.gov/pml/x-ray-form-factorattenuation-and-scattering-tables.

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Oxygen K-edge X-ray Absorption Spectroscopy of Molecular Oxygen
Adsorbed on Lipid Bilayers
F. Kumaki1,2, M. Nagasaka3,4, Y. Kinjo5, R. Tero5, Y. Okano3, M. Fujimoto3,4 and J. Adachi1,2Institute of Materials Structure Science, High Energy Accelerator Research Organization, Tsukuba 305-0801, Japan
2
School of High Energy Accelerator Science, The Graduate University for Advanced Studies (SOKENDAI),
Tsukuba 305-0801, Japan
3
Institute for Molecular Science, Okazaki 444-8585, Japan
4
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
5
Toyohashi University of Technology, Toyohashi 441-8580, Japan1

Ⅲ-3

Some porphyrin complexes, such as the photosynthetic
pigment chlorophyll, are known to produce singlet
oxygen (1O2) by transferring energy to oxygen moleculesthat is triplet oxygen (3O2) in the surrounding environment
at the photo-excitation and relaxation processes due tolight absorption. Singlet oxygen is high-reactive. It cancause damage to biological cells or the sample itself inspectroscopic experiments. In generally, the sample
solution is bubbled with argon gas to displace thedissolved oxygen to avoid the generation of singlet
oxygen at the measurement of a spectrum in visible rightregion. On the other hand, the process of singlet oxygen
generation accompanying with photoexcitation andrelaxation processes of photosensitizers such as
porphyrin complexes is applied in cancer treatment as
photodynamic therapy [1]. Elucidating the dynamics of
singlet oxygen production in such a wet environment is
expected to contribute to further research of chemistry
and medicine.
We designed the way to measure directly the electricstates of singlet oxygen occurred in solution by O Kedge x-ray absorption spectroscopy (XAS). Timeresolved XAS measurement system with synchronizedsoft X-rays pulse (530 eV, 128 ps) and visible laser
pulses (400 nm, 130 fs) have been developed and will
be applied. The lifetime of singlet oxygen in liquid is
3 μs [2], which can be measured with the 128 ps time
resolution of synchrotron radiation. In this measurement,
a method to measure a dissolved oxygen spectrum wasestablished as a preliminary step for XAS measurementsof singlet oxygen.
The XAS spectrum was measured by using thesolution XAS measurement system at UVSOR BL3U[3]. The liquid cell consists of a solution layer
sandwiched between two Si3N4 membranes. Lipid
bilayers ware formed on Si3N4 membranes by pumping
the lipids vesicle aqueous solution to flow into the liquidcell. Then, dissolved oxygen was kept on the lipid
bilayers by continuously pumping the buffer solution(NaCl 100 mM, HEPES 25 mM) bubbled with oxygengas at a flow rate of 100 µl/hr. By increasing the heliumpressure in the sample chamber and making the solution
layer as thin as possible, the spectrum that has theemphasized peak of dissolved oxygen on the lipid
bilayer was measured. In the measurement of singlet
oxygen, chlorophyll a, added as a photosensitizer to thelipid bilayer, is photoexcited by visible laser with 400
nm which is SH (second order harmonic) of Ti:sapphirelaser. We are planning to measure an O K-edge XAS
spectrum of the singlet oxygen produced by the energy
transfer at the relaxation process of the photo-excitedtriplet state of chlorophyll a.
Figure 1 shows the O K-edge XAS spectrum ofliquid bilayer measured in this experiment. The peakat around 531 eV corresponds to dissolved oxygen
absorbed on lipid bilayer which is in the ground state.
Since the O K-edge XAS spectrum of water is inhigher energy region than 533 eV, the spectrum of
dissolved oxygen can be clearly distinguished.

Fig. 1. The O K-edge XAS spectrum of the lipid
bilayer. The peak around 531 eV corresponds to a peakof dissolved oxygen absorbed on the lipid bilayer.

[1] M. Ethirajan et al., Chem. Soc. Rev. 40 (2011) 340.
[2] C. A. Long and D. R. Kearns, J. Am. Chem. Soc. 97(1975) 2018.
[3] M. Nagasaka et al., J. Electron Spectrosc. Relat.
Phenom. 224 (2018) 93.

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Position-Sensitive Soft X-ray Absorption Spectroscopy of Carbon-based
Catalysts for Redox Flow Battery
E. Hosono1,2,3, D. Asakura1,2,3, H. Yuzawa4, T. Ohigashi4,5 and A. Ohira1,2,3

Global Zero Emission Research Center, National Institute of Advanced Industrial Science (AIST),
Tsukuba 305-8569, Japan
2
Research Institute for Energy Conservation, AIST, Tsukuba 305-8565, Japan
3
AIST-UTokyo Advanced Operando Measurement Technology Open Innovation Laboratory (Operando-OIL),
Kashiwa 277-8565, Japan
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
5
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan1

Utilization of renewable energy such as solar celland wind power is indispensable for reduction of CO2
emission and realizing zero emission society. To stably
use the renewable energy in practical use, developmentof large-scale energy storage devices is needed. Redox
flow battery (RFB) is one of the candidates [1] as well
as Li-ion battery (LIB).
The electrolyte solutions of RFB play a role on theredox reaction as both positive and negative electrodes(i.e., catholyte and anolyte) (Fig. 1), which is different
from LIB where the solid-state electrodes (cathode andanode) exhibit the redox reaction. The carbon-based
electrodes are soaked in electrolyte solutions and H+ inthe solutions can move through an ion-exchange
membrane between the two electrodes bycharge/discharge (Fig. 1). To raise the efficiency of theredox and H+ conduction, the performance of carbonbased catalysts combined with the electrodes should be
investigated. Electronic-structure analysis using soft
X-ray absorption spectroscopy (XAS) is suitable forstudying the performance. Then, scanningtransmission X-ray microscopy (STXM) provides not
only the information of electronic structure, but also its
distribution with a high spatial resolution (<100 nm).
Thus, we adopted STXM at the C K-edge to carbonbased catalysts for RFB. The STXM measurements
were conducted at BL4U, UVSOR.
Figure 2 shows a pinpoint C K-edge absorption
spectrum (in transmission mode) of a selected area for
a graphene sample. The peaks at 285.4 and 291.8 eV
in Fig. 2 correspond to π* and σ* peaks, respectively[2,3,4]. The weak π* peak compared to the σ* peak issimilar to the spectrum for graphite with normal
incidence [2,3], which suggests that the graphene
layers stack along the X-rays. Almost all the area of thegraphene particle in the STXM image showed similar
XAS line shape. This is important information because
the catalytic performance would be dependent on theorientation of stacking. Furthermore, the spectrum
shows no peak between the π* and σ* peaks, indicating
almost no contamination.
In future, we will try in situ/operando STXM byconstructing a special cell for RFB.

Ⅲ-3

Fig. 1. A schematic picture of RFB using vanadium.

Fig. 2. A pinpoint C K-edge XAS spectrum of a specificarea (~350 nm × ~180 nm) of the graphene sample.

[1] For example, A. Z. Weber et al., J. Appl. Electrochem.
41 (2011) 1137.
[2] M. T. Chowdhury et al., Phys. Rev. B 85 (2012)
115410.
[3] M. Abbas et al., Appl. Phys. Lett. 87 (2005) 051923.
[4] A. Li et al., Electrochim. Acta 276 (2018) 153.

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Investigating Electrochemical Reactivity on Ni(OH)2 Electrocatalyst in
Alkaline Electrolytes
J. Kim1 T. Ohigashi 2,3 and J. Lim1

Department of Chemistry, Seoul National University; 1 Gwanak-ro, Gwanak-gu, Seoul 08826, Republic of Korea
2
Editorial Board, UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan3
School of Physical Sciences, The Graduate University for Advanced Studies (SOKENDAI), Okazaki 444-8585, Japan
1

Ⅲ-3

During the electrochemical reaction, the phasetransformation of energy storage/conversion materials
accompanies intrinsic variation on physico-chemical
properties. In particular, the energy conversion materials(catalysts) in aqueous system suffer severe chemical
and/or morphological changes during reaction. [1]These changes are governed by the thermodynamics
that the material exists as a possible stable phaseaccording to pH or potential. In dynamic condition, thelocally generated chemical equilibrium induces theevolution of electrochemical active phase in nanoscale,
which are responsible for electro- catalytic activity andstability.
Among various energy conversion materials,
Ni(OH)2, which exhibits superior oxygen evolution
reaction (OER) activity, experience multiple phasetransformation via dehydrogenation process during
OER. [2] Specifically, as hydrogen atom is extracted
from the lattice, -Ni(OH)2 (Ni2+) can convert to moreoxidized phase such as -NiOOH (Ni3+) and -NiOOH(Ni3.6+), and the OER activity is highly dependent onthese high valence state of Ni phases. Additionally,lattice oxygen atoms also play an important role in the
OER due to bond formation /breaking process withactive metal site. An understanding of the active phaseevolution and the coordination of oxygen atom withactive metal site is a fundamental prerequisite fordesigning improved OER catalysts, but it remains a
crucial challenge to identify the generation andevolution of nanoscale active phase spatially due to alack of characterization technique. To investigate theevolution of OER active phase (-NiOOH or -NiOOH),
we implemented operando scanning transmission X-ray
microscopy (STXM) to track the change in Ni oxidation
state that indicates the phase transformation of Ni(OH)2during OER at the Pohang Light Source STXM
beamline 10A1.
Distinctive feature in the phase transformation of Ni(OH)2 is that Ni3.6+ phases, -NiOOH at 1.70 V versus
reversible hydrogen electrode (RHE), are reduced at 1.8
V and 1.9 V versus RHE, where OER is highly occurred.
(Fig. 1) From this observation, we speculate that there
are two possibilities. First, potassium ion (K+) inelectrolyte could intercalate into the slab, leading to
reduction of the Ni oxidation state owing to the charge
neutrality. [2] Second, during OER, oxygen vacancies
are generated in the catalyst. [3] To confirm thegeneration of oxygen vacancies in high anodic potential
region, we conducted ex situ STXM measurement of -Ni(OH)2 at UVSOR BL4U for investigating the change
in O K-edge absorption spectra.
Figure 2a shows particle-averaged O K-edge spectraof -Ni(OH)2 at different potentials, revealing that the
pre-peak A (532 eV), assigned to the hybridization of Ni
3d and O 2p orbitals states with eg orbital symmetry andthe d7 (Ni3+) electron configuration, is varied at different
potentials. [3] In particular, the intensity of peak A
suddenly decreases at 1.65 V, suggesting the return ofelectrons to Ni site. It can be attributed to the formationof oxygen vacancies and the decreased oxidation stateof Ni site. From our results, we conclude that generationof the oxygen vacancy during OER could induce
reduction of the active phase (-NiOOH), consistent
with our operando STXM results.
OCV

1.40 V

1.50 V

1.60 V

1.70 V

1.80 VNi2+

1.90 V

1.10 V

Ni3.6+

500 nmFig. 1. Operando chemical composition mapping imagesof -Ni(OH)2 electrocatalyst during OER.
(Unpublished)abFig. 1. a. Voltage-dependent particle-averaged O Kedge STXM-XAS spectra. b. Intensity of peak A at
different potentials.

[1] Chung, D.Y., Lopes, P.P., Farinazzo Bergamo Dias
Martins, P. et al., Nat Energy 5 (2020) 222.
[2] Mario González-Perea et al., ECS Trans. 36 (2011)
299.
[3] Kang, J., Qiu, X., Hu, Q.et al., Nat Catal. 4 (2021)
1050.

12016 Ⅲ03-

BL4B

Ⅲ -3. Chemistry

BL4B

Quadruple Auger Decay of the Xe 3d5/2 Core-Hole State Investigated byMultielectron−Ion Coincidence Spectroscopy
Y. Hikosaka

Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japanthe state energies of the Xe4+ 4d−15p−3 levels measured
from 2P1/2 or 2P3/2 of 5p−5, and thus many different Xe4+
4d−15p−3 levels are formed through the third-step Auger
decay of Xe3+ 4d−25p−1 → Xe4+ 4d−15p−3.
0Kinetic energy of slower electron (eV)20Counts

Decay from 4d-25p-1

15

250 500
20

15

4d-25p-1→ 4d-15p-3

10

10
-1

-3

4d 5p
→ 5p-5
5

0

5

0

5

10

15

20

25

30

35

Kinetic energy of slower electron (eV)

Magnetic bottle electron spectrometer is a very
efficient electron spectroscopic method, utilizing an
inhomogeneous magnetic field to capture all theelectrons formed by photoionization. Its use enables us
to perform multielectron coincidence spectroscopy very
effectively. While the electrons captured over 4πsteradian solid angle are guided to an MCP detector
ending a long flight path, ions formed together withelectrons can be also detected with the same detector, byapplying a pulsed electric field to the photoionization
region [1]. To improve the efficiency in multielectronion coincidence measurements, an MCP detector with alarge open area ratio (nominally 90 %) was recently
introduced in our magnetic bottle electron spectrometer[2].
The usefulness of this improved coincidence
efficiency is demonstrated by a six-fold coincidence
about the quadruple Auger decay of the Xe 3d5/2 corehole state. Figure 1 shows energy correlations between
the two Auger electrons emitted from Xe3+ 4d−25p−1,
which was derived from six-fold coincidences including
the 3d5/2 photoelectron, first-step Auger electron
forming 4p-14d-1, second-step Auger electron forming
4d−25p−1, and Xe5+. The additional coincidence with the
product Xe5+ ions effectively isolates the events
associated with the quadruple Auger decay. On the twodimensional map in Fig. 1, remarkable island structures
are observed in the area indicated by a square. The fasterand slower electrons forming the island structures are
assignable to the third-step Auger decay of Xe3+
4d−25p−1 → Xe4+ 4d−15p−3 and the fourth-step Auger
decay of Xe4+ 4d−15p−3 → Xe5+ 5p−5, respectively.
Essentially the same coincidence structure wasobserved in a previous multi-electron coincidence
measurement [3]. Note that the previous observation
was occurred in correlations between two electronsobserved in coincidence with the 3d photoelectron andfirst-step Auger electron, and thus as four-electron
coincidences.
One may see that the island structures lie on several
diagonal lines defined by x + y = constant. This isbecause the sums of the two Auger electrons correspondto the energy differences between Xe3+ 4d−25p−1 and
Xe5+ 5p−5 levels. Here, the appearance of multiple
diagonal lines is due to the contributions from different
levels of initial 4d−25p−1 and final 5p−5. The right panelof this figure shows the projection of the island
structures toward the y axis of the two-dimensional map.
The projection curve exhibits sharp peaks due to thefourth-step Auger decay of Xe4+ 4d−15p−3 → Xe5+ 5p−5.
The kinetic energies of the sharp peaks correspond to0

Kinetic energy of faster electron (eV)Fig. 1. Energy correlation map between two Auger
electrons ejected in the quadruple Auger decay of theXe 3d5/2 core-hole state, derived from six-foldcoincidences including the 3d5/2 photoelectron, firststep Auger electron forming 4p-14d-1, second-stepAuger electron forming 4d−25p−1, and Xe5+ ion, andthus it displays the energy correlation between the twoAuger electrons emitted in the decay of Xe3+ 4d−25p−1.
The right panel plots the projection of the coincidence
counts in the region x = 14-24 eV toward the y axis,
which exhibits the structures resulting from the fourthstep Auger decay of Xe4+ 4d−15p−3 → Xe5+ 5p−5.

[1]Y. Hikosaka and E. Shigemasa, Int. J. Mass Spectrom.
439 (2019) 13.
[2] Y. Hikosaka, J. Electron Spectrosc. Rel. Phenom.
255 (2022) 147158.
[3] I. H. Suzuki et al, J. Phys. B: At. Mol. Opt. Phys. 44(2011) 075003.

12117 Ⅲ03-

Ⅲ-3

BL4B
Ⅲ -3. Chemistry

BL4B

Ion Branching Ratio for the Xe 4p Auger Decay Studied by
Photoelectron−Ion Coincidence Spectroscopy
Y. Hikosaka

Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan

Ⅲ-3

Binding energy of Xe+ (eV)
250

200

150

100

250000Intensity (arb. units)

Photoelectron spectroscopy has revealed an anomalous
photoelectron structure of the 4p core-hole state in Xe[1]. In a photoelectron spectrum, the expected 4p1/2
photoelectron line is dissolved and no longer visible,
whereas the 4p3/2 structure consists of several finecomponents. These observations imply the breakdownof the independent particle model, resulting from thestrong interaction between the 4p-1 and 4d-2nf/4d-2εf
configurations [2]. In this work, the ion branching ratio
associated with the Auger decay of the 4p core-hole stateis inspected. A magnetic bottle electron spectrometer withion detection capability [3,4] was employed in this study,
to conduct an efficient photoelectron-ion coincidence
measurement. The measurement was implemented at a
photon energy of 391.7 eV (bandwidth of ~0.2 eV), i.e.
~240 eV above the 4p threshold.
Figure 1 presents a photoelectron spectrum of Xe andthose filtered by coincidences with different XeZ+ ions
(Z = 1-6). Photoelectron structures associated withejections of electrons from the N and O shells are
exhibited in these spectra. The ion detection efficiencies
were compensated for the spectral intensities of thecoincidence spectra; thus, the relative intensities ofindividual photoelectron structures in these spectra
reflect the ion branching ratios associated with the
decays of these core-hole states. The ion branchingratios of the individual core-holes states were alreadystudied by Eland et al. with the same coincidence
method [5].
The photoelectron spectrum (Fig. 1 top) shows the 4p
photoelectron structure consisting of a peak around a
kinetic energy of 245 eV and a remarkable shoulder inthe lower kinetic energy side. As already pointed out by
Eland et al. [5], the determination of the ion branchingratio of the 4p decay is not straightforward, because thedetermined ratio varies greatly with the photoelectron
range considered. When only the peak range around a
kinetic energy of 245 eV is considered, the formation of
Xe3+ is dominant and a sizable Xe4+ formation isprobably identified. This is consistent with a multielectron coincidence study which reports a dominant
Xe3+ formation for the main 4p photoelectron peak [6]and also with a recent calculation [7]. On the other hand,the shoulder part of the 4p photoelectron structure
mainly produces Xe4+ ion. The shoulder part can be
ascribed to double photoionization into the 4d-2 states,
which is enhanced by the virtual super Coster-Kronigtransition [2] of 4p-1 → 4d-2εf over several tens of electron
volts [8]. The formed 4d-2 states dominantly proceed tosequential fillings of the double 4d core-holes [8],resulting in the dominant formation of Xe4+ ion.

50

0

4d-1

2000001500004p-1

100000

4s-1

50000
0

sat.

5p-1
5s-1

Xe+
Xe2+
Xe3+
Xe4+
Xe5+
Xe6+
150

200

250

300

350

400

Kinetic energy of electron (eV)Fig. 1. Photoelectron spectrum of Xe measured at a
photon energy of 391.7 eV, and coincidence spectra
obtained by filter with different XeZ+ ions (Z = 1-6).
The intensities of the coincidence spectra werecorrected by the ion detection efficiencies.

[1] S. Svensson et al., Phys. Scr. 14 (1976) 141.
[2] G. Wendin and M. Ohno, Phys. Scr. 14 (1976) 148.
[3] Y. Hikosaka and E. Shigemasa, Int. J. Mass Spectrom.
439 (2019) 13.
[4] Y. Hikosaka, J. Electron Spectrosc. Rel. Phenom. 255(2022) 147158.
[5] J. H. D. Eland et al., J. Phys. B 48 (2015) 205001.
[6] Y. Hikosaka et al., Phys. Rev. A 76 (2007) 032708.
[7] Z. Liu et al., Chin. Phys. Lett. 38 (2021) 023201.
[8] Y. Hikosaka et al., Phys. Rev. Lett. 98 (2007) 183002.

12218 Ⅲ03-

BL4B

Ⅲ -3. Chemistry

BL4B

Electronic Structure Analysis of Ni Complex Bearing N-Heterocyclic
Carbene Ligand Using Ni L2,3-edge X-ray Absorption Spectroscopy
Y. Uetake1,2, Y. Yamauchi1 and Y. Hoshimoto1

Division of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita 565-0871, Japan
Innovative Catalysis Science Division, Institute for Open and Transdisciplinary Research Initiatives (ICS-OTRI),
Osaka University, Suita 565-0871, Japan
1

2

Recently, we have synthesized a Ni(0) complex
bearing tris(pentafluorophenyl)borane (BCF) as anelectron accepting Z-type ligand and N-heterocycliccarbene as an ancillary ligand (1). Single crystal X-ray
diffraction (SC-XRD) analysis of 1 revealed that itexhibits a square-planer structure typical of Ni(II)complexes, unlike the tetrahedral geometry that iscommon for Ni(0) complexes probably due to thesterically demanding BCF ligand. Interested in theelectronic structure of 1 which contradicts the ligand
field theory, we have performed Ni K-edge X-ray
absorption spectroscopy (XAS) of this complex at
SPring-8 BL14B2 beamline and found that this complex
possessed low-valent Ni(0)-like electronic structure.
However, since Ni K-edge XAS basically corresponds
to the electron transitions from 1s to a vacant 4p orbital
because of the Fermi’s golden rule [1], it is difficult toclarify the details of the electronic structure of 3dorbitals which determines the characteristics of metal
complexes. In this study, Ni L2,3-edge XAS experimentsof the Ni-BCF complex were investigated.
Ni L2,3-edge XAS experiments were performed at
the BL4B beamline using partial fluorescent yields(PFYs) method with silicon drift detector (SDD). A
stainless-steel sample holder with double-sided
conductive carbon tapes was attached to a transfer
vessel, which was connected to a glovebox. The insideof the glovebox was evacuated using a rotary pump forat least 30 min, and then, filled with argon gas. The
powder sample was applied on a carbon tape, andrubbed with the back of a spatula. After storing thesample holder in the vessel, the gate valve was closed.
The vessel was detached from the glovebox, and then,attached to the main chamber. The air in the mainchamber was evacuated by a rotary pump, and the gate
valve was slowly opened after the pressure level
reached in the order of 10–3 Pa. A turbo-molecular pump
was then activated to create a high vacuum environment.
XAS measurements were performed under the pressureless than 5×10–5 Pa.
Ni L2,3-edge XAS data of 1, 2 and 3 are shown in Fig.
1. Although the peak intensity of 1 was different from
Ni(II) complex 3, the peak position of 1 was similar tothat of 3 which has octahedral ligand field rather thantetrahedral Ni(0) complex 2, indicating the intrinsic
geometrical similarity between the square-planer andthe octahedral. Meanwhile, slightly intense first peak of
1 observed at 852.5 eV was assigned as the electrontransition from 2p3/2 to 3dx2-y2 orbital. This result

indicated the low d-electron occupancy in 3dx2-y2 level
due to the σ-backdonation from Ni 3dx2-y2 orbital tovacant p orbital of BCF. In addition, the peak area of 1
(15.5) was closer to 2 (11.5) rather than 3 (25.3) (Table
1). Considering that the peak area reflects the transition
probabilities of the electrons [2,3], the d-electron
occupancy of 1 would be closer to the Ni(0) state rather
than to the Ni(II) state, which is consistent with the Ni
K-edge XAS experiment. In addition, the slight increaseof the L2,3-edge intensity of 1 would reflect the polarizedNiδ+–Bδ– bonding state.

Ⅲ-3

Fig. 1. Ni L2,3-edge XAS data of 1, 2 and 3.
Table 1. Peak area of Ni L2,3-edge XAS data after
normalization.
Peak area
L3
L2
L3 + L2
1
10.5
5.1
15.5
2
7.8
3.7
11.5
3
17.3
8.0
25.3
[1] P. M. A. Dirac, Proc. Roy. Soc. A 114 (1927) 243.
[2] E. I. Solomon, S. P. Cramer et al., J. Am. Chem. Soc.
115 (1993) 2968.
[3] K. M. Lancaster et al., J. Am. Chem. Soc. 141 (2019)
18508.

12319 Ⅲ03-

BL5B
Ⅲ -3. Chemistry

BL5B

Evaluation of Absorption Stability of a Hydrogen Absorption Cell
M. Taguchi1, M. Kuwabara1, T. Katsumata1, M. Tateyama1, K. Yoshioka2,3, Y. Suzuki3,
K. Goda4, K. Inoue4, A. Tomioka4 and A. Yamazaki4

Department of Physics, College of Science, Rikkyo University, Tokyo 171-8501, Japan
Department of Complexity Science and Engineering, Graduate School of Frontier Sciences, The University of Tokyo,
Chiba 277-8561, Japan3
Department of Earth and Planetary Science, Graduate School of Science, The University of Tokyo,
Tokyo 113-0033, Japan
4
Department of Earth and Planetary Physics, Faculty of Science, The University of Tokyo, Tokyo 113-0033, Japan
1

2

Ⅲ-3

A hydrogen absorption cell (HAC) is a unique
optical filter which enables us to estimate density andtemperature distributions and an isotope ratio ofhydrogen atoms escaping from a planetary atmosphereby detecting a hydrogen Lyman α emission of aplanetary corona. The HAC is especially suitable for a
payload of a planetary mission because of its small sizeand light weight. However, no measurement of aplanetary corona by a HAC has been successful so far.
Development of a newly designed HAC has beenproceeded by the proposers, and it has been decided
that the HAC is on board Comet Interceptor which isan ESA mission to investigate an atmosphere of a comet.
Absorption efficiency of the HAC has been improved,
but its lifetime has not yet been confirmed. Absorption
performance should be highly stable during the mission
lifetime of several years. Here we present a result of anexperiment in which absorption stability of a protomodel HAC was evaluated using the spectrometer at
BL5B of UVSOR.
The HAC and a Kr cell were installed in the beamline.
The Kr cell, which contains Kr gas with a pressure of
500 Pa, was used for wavelength calibration of thespectrometer. The grating and mirror combination of“G3M5” was selected. The slit width and the pinhole
diameter were 0.01 mm and 1 mm, respectively.

Dimension of the HAC isφ35 mm and L40 mm.
Pure hydrogen gas filtered by a palladium filter with apressure of 200 Pa was filled in the HAC. One of thefilaments on the HAC was used for this stability test.
Filament voltage was fixed at 5.73 V, which heats up
the filament at a temperature of approximately 1800 K.
A set of data consists of four spectra obtained withcombinations of the filament on and off and the beamon and off from 121.1 nm to 122.0 nm with a scan stepof 0.01 nm. It took approximately 70 min to acquire aset of data.
Figure 1 shows 8 absorption spectra of hydrogen
Lyman α consecutively obtained by the HAC during a
beamtime of 12 h. The depth of absorption almost
unchanged, though the filament current slightly
decreased from 0.170 A at the beginning to 0.167 A atthe end. Accordingly, the filament temperature
estimated from the voltage and current slightly
increased. During the beamtime of four weeks thisfilament was activated for longer than 30 h, but nosignificant degradation was observed.
All the absorption spectra show an increasing trend
from the shorter wavelength to the longer wavelength.
The reason for this trend is unclear, but it might berelated to any variation in the environment.

Fig. 1. Absorption spectra of hydrogen Lyman α consecutively obtained by a HAC under the same condition ofgas pressure and filament voltage with the same filament.

12420 Ⅲ03-