Ⅲ-3
Chemistry
ChemistryBL1UⅢ -3. Chemistry

BL1U

Controlling the Orbital Alignment in Atoms using Circularly Polarized
Radiation Wave Packets
T. Kaneyasu1,2, Y. Hikosaka3, M. Fujimoto2,4, H. Iwayama2,4 and M. Katoh2,5

SAGA Light Source, Tosu 841-0005, Japan
Institute for Molecular Science, Okazaki 444-8585, Japan
3
Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, 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

We report on a new application of the circularly
polarized radiation provided by a helical undulator ata synchrotron light source - the coherent control of
excited state alignment [1]. Our method is based on theuse of undulator radiation to create longitudinallycoherent wave packets with attosecond-controlled
spacing [2]. The performance of our scheme isdemonstrated by the photoexcitation of helium atoms
in the extreme ultraviolet wavelength region by using
the temporal coherent control technique.
The experiment was carried out at the beamline
BL1U using the tandem undulator consisted of twin
APPLE-II devices. We set the upstream anddownstream undulators to provide left-circularpolarization (LCP) and right-circular polarization(RCP), respectively. The central photon energy of thefundamental radiation was adjusted to ~24 eV, atwhich the period of the radiation is ~171 as. Each
relativistic electron in the bunch which passes though
the tandem undulator emits a pair of wave packets
whose waveforms are well-characterized as timeseparated 10-cycle oscillations. The spacing between
the wave packets was tuned with attosecond precisionby the phase shifter magnet.
Figure 1 illustrates the helium atom interacting withthe radiation wave packets from the tandem undulator.
As a result of the sequential interaction with the wave
packets, helium atom is excited to the 1s6p coherent
superposition state (transition frequency of ω), which
consists of the Mj=±1 magnetic substates associatedwith the first (LCP) and second (RCP) parts of the
wave packet pair, following the selection rules for
dipole transitions. In an orbital picture, the 6p± orbitals
are coherently superposed, forming a 6p orbitalaligned in the xy-plane. The orbital alignment is
controlled by the delay time, where the tilt angle is set
to ωτ/2 with respect to the x-axis. The detector setup
allows us to determine the alignment of the 6p orbital
because the fluorescence photons are preferentiallyemitted perpendicular to the alignment axis.
Figure 2 shows the fluorescence yield measured asa function of delay time in decays from the 1s6p to the
1s2s states, revealing a clear sinusoidal modulation.
Reflecting the spatial distribution of the dipole
emission as shown in the top panel of Fig. 2, we can
expect the signal intensity oscillates at the resonant
frequency of the 1s6p excited state depending on the

delay time. The observed oscillation shows highvisibility and is well reproduced by a sinusoidal curve.
This supports the applicability of circularly polarized
undulator radiation to control excited state alignment
based on the temporal coherent control technique.

Ⅲ-3

Fig. 1. (a) Interaction between the radiation wave
packet pair and helium atom. The fluorescencephotons are detected by the photomultiplier tube. (b)The helium atom is excited into the 1s6p superposition
state which consists of the Mj=±1 substates associatedwith the first (LCP) and second (RCP) parts of the
wave packet pair.

Fig. 2. Fluorescence yield measured as a function of
the delay time. The gray circles are measured data andthe red line shows the theoretical curve.
[1] T. Kaneyasu et al., Phys. Rev. Lett. 123 (2019)
233401.
[2] Y. Hikosaka et al., Nat. Commun. 10 (2019) 4988.

103
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Ⅲ -3. Chemistry

BL3U

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

Ⅲ-3

H. Takaya1, M. Nagasaka2 and K. Kashimura3

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
2
Faculty of Engineering, Chubu University, Kasugai 487-8501, Japan

We have found that iron complexes of FeX2SciOPP(X = Br or Mes) bearing a bulky phosphine ligand
SciOPP showed excellent catalytic activities toward thecross-coupling of organometallic reagents of Mg, B, Al,
and Zn with various aryl halides [1,2]. Such iron-based
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 theconventional solution-phase NMR analysis cannot be
used due to the paramagnetic nature of organoiron
species along with the large paramagnetic shift and peakbroadening in NMR spectrum. L-edge XAS oftransition-metal catalysts has been expected to be highly
useful to investigate the electronic structure of 3dorbitals which provide essential information to elucidate
how to work the catalyst. However, solution-phase Ledge XAS measurement is generally difficult because
the measurement has to be performed under a vacuum
condition where the solution sample is vaporized withvigorous boiling. In this project, we used the speciallydesigned flow-cell for the solution-phase L-edge XAS
measurement of homogeneous organic solution of ironcomplex catalysts. In BL3U, a stainless-steel flow cellhas been used for various experiments, but we shouldcarefully avoid contamination of iron species from theenvironment. For this reason Prof. Nagasaka newly
designed and prepared 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 with an excellent chemical resistance toward thevarious organic solvents such as THF, CH2Cl2, andbenzene, these often used in iron-catalyzed crosscoupling 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, and connected
to a syringe pump through a Teflon tube. The THF
solution samples of iron catalyst and isolate catalyticintermediates of FeX2SciOPP 1–3 (X = Br or Mes) wereprepared in an argon-filled glovebox, because thesolution of iron complexes are quite sensitive to oxygen
and water, and immediately react to give iron oxide andhydroxide. The XAS measurement was successfully
carried out under a flow condition (flow rate: 50–200μL/h) to give L-edge NEXAFS of 1–3 without theundesired baseline shift by the static electricity (Fig. 2.).
However, the penetration of helium gas into the cellcausing a bubbling noise could not be perfectly
controlled. To solve this problem, Viton O-ring ischanged to a fluorosilicone polymer with improving theflow line design and tube connection. This improved
cell is testing in 2020 experiment.

Fig. 1. Photos of the PEEK-made flow cell.

Fig. 2. Solution-phase NEXAFS spectrum ofFeX2(SciOPP) in THF.
[1] H. Takaya and M. Nakamura et al., Bull. Chem.
Soc. Jpn. 88 (2015) 410.
[2] R. Agata, H. Takaya, and M. Nakamura et al., Bull.
Chem. Soc. Jpn. 92 (2019) 381.

104
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Ⅲ -3. Chemistry

BL1U

Supramolecular Chirality Induction by Optical Vortex UV Light toMagnetic Azo-metal Complexes
T. Akitsu1, S. Yamazaki1, M. Yoshida1, T. Haraguchi1, M. Fujiki2,
M. Fujimoto3 and M. Katoh3,4Faculty of Sciences, Tokyo University of Science, Tokyo 162-8601, Japan
Graduate School of Materials Sciences, NAIST, Ikoma 630-0192, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
HiSOR Facility, Hiroshima University, Higashi-Hiroshima 739-0046, Japan1

2

For several years, we have studied on photochemicalmaterials using optical vortex UV light have attracted
attention. In contrast to circularly polarized light(associated with spin angular momentum), a lightvortex having a spiral wave front (associated withorbital angular momentum) may provide mechanicaltorque onto the surface of (photofunctional) materials
irradiated. In this context, we attempted molecularorientation control by irradiating linearly and/or
circularly polarized (and optical vortex) UV light topolymer films containing (achiral) dinuclear Schiff basemetal complexes without photoisomerization moiety inprevious study [1,2]. Herein, we have designed newmetal complexes having rigid Y-shaped structure withphotoisomerization moiety expected to occur Weigert
effect to be aligned by polarized UV light. Newly
prepared PMMA films from DMF solvent were also
employed for enhancing molecular orientation
phenomenon induced by several types of UV lightirradiation not on the surface but even in the films.
By using laboratory light source, linearly or
circularly polarized UV light was irradiated to the
PMMA films containing the metal complexes. For
example, after linearly polarized UV light irradiation,
optical anisotropy of Zn or Cu complexes-PMMA
sample was observed as depicted in Fig. 2. Similarly,
after circularly polarized UV light irradiation, new CD
bands appeared, which suggested chirality attributed
not to achiral molecules but to supramoleculararrangement induced by light. Thus, the Zn complexPMMA was more sensitive to light.
At UVSOR, optical vortex with l = +1, -1 orbital
angular momentum at 280 nm from linearly polarized
light was irradiated to the same sample. CD spectra(Fig. 3) were analyzed with sine curve fiting to extract
major linearly polarized light component and minor
orbital angular momentum component.

Fig. 1. Molecular structures of metal complexes (M=Cu(II) and Zn(II)).

Fig. 2. Angular dependence of absorbance of polarized
UV-vis spectra at 385 nm for the Zn complex-PMMA
sample.

[1] H. Nakatori, T. Haraguchi and T. Akitsu, Symmetry
10 (2018) 147.
[2] M. Takase, S. Yagi, T. Haraguchi, S. Noor and T.
Akitsu, Symmetry 10 (2018) 760.
Fig. 3. CD spectra for the Zn complex-PMMA sample
after optical vortex irradiation. KBr disk were rotated atfive points to cancel artifact CD peaks.

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Ⅲ-3

BL1U
Ⅲ -3. Chemistry

BL1U

Time-Domain Ramsey Interferometry on Rydberg-Electron Wave Packets
Generated in Helium Atoms
Y. Hikosaka1, T. Kaneyasu2,3, M. Fujimoto3, H. Iwayama3 and M. Katoh3,4Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
2
SAGA Light Source, Tosu 841-0005, Japan
3
Institute for Molecular Science, Okazaki 444-8585, Japan
4
Hiroshima Synchrotron Radiation Center, Hiroshima University, Higashi-Hiroshima 739-0046, Japan1

Ⅲ-3

Quantum state control of matter by the coherence oflight has attracted great interest in various fields suchas physics, chemistry, and information processing. The
forefront of this coherent control research is rapidly
evolving to the extreme ultraviolet wavelength range
and attosecond time resolution, thanks to thedevelopments of laser high-harmonic generations andseeded free electron lasers. On the other hand, while
synchrotron radiation is high-brightness light covering
a wide wavelength range up to X-rays, its longitudinalcoherence is significantly lower than that of a laser.
Thus synchrotron radiation has not been considered asa tool for coherent control. We demonstrate here thecapability of synchrotron radiation to perform
coherent control by achieving time-domain Ramseyinterferometry on Rydberg wave packets generated in
He atoms.
Our scheme for the coherent control by synchrotron
radiation uses light wave packet pairs contained in theradiation pulses from two undulators [1,2]. The
experiments were performed at the beamline BL1U.
The two APPLE-II undulators inserted in series in the
U1 straight section of the storage ring were both set tolinear polarization mode, and light wave packet pairs of
extreme ultraviolet (central photon energy of 24 eV and
10% bandwidth) were emitted. The delay time between
the light wave packets was adjusted with an attosecond
precision in the range of 2-50 fs, by the three-pole
wiggler magnet installed between the two undulators.
The central part of the undulator radiation was cut out
by an aperture with a diameter of 0.4 mm at 8.2 m

downstream from the downstream undulator, andirradiated with He gases. The bandwidth of the undulator
spectrum covers the Rydberg states with principal
quantum numbers from 3 to ∞. Visible/ultraviolet
fluorescence emitted in the decays of the populated
Rydberg states in He was detected by a photomultiplier
tube.
Figure 1 shows the total fluorescence yieldmeasured as a function of the delay time between thelight wave packets. It is observed that the fluorescence
yield, reflecting the amount of Rydberg states
populated by the irradiation, oscillates with a period of
about 170 as and its amplitude is modulated. The delay
time response of the fluorescence yield is understoodin terms of interference of the Rydberg-electron wave
packets generated by the light wave packet pair. Whenthe fluorescence from individual Rydberg states was
selected in the observation, the relative fluorescenceintensities of these states showed remarkable changes
depending on the delay time [1]. This observation
proves that the populations of the Rydberg states canbe controlled by tuning the delay of the light wave
packet pair.
[1] Y. Hikosaka et al., Nat. Commun. 10 (2019) 4988.
[2] T. Kaneyasu et al., Phys. Rev. Lett. 123 (2019)
233401.

Fig. 1. Intensities of fluorescent photons from He, measured as a function of the time delay between the lightwave packets generated by a tandem undulator [1]. Delay time of the horizontal axis is measured from the original
delay (~2.1 fs) between the light wave packets.

106
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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 Science, 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

Photoelectron circular dichroism (PECD) is
expected to be a powerful tool for chiral recognition
because of the high efficiency due to electric dipole
interaction of chiral molecules with radiation. The
PECD emerges as forward-backward asymmetry in
the photoelectron scattering distribution ofenantiomers with respect to propagation of circularpolarized light. The origin of PECD has been simply
described as an incomplete compensation of thescattering amplitudes of partial photoelectron waves
due to the chiral molecular framework. Although agood agreement of the experiments and theoreticalmodel calculations was shown for typical chiralmolecules in the previous studies with VUV light, arecent finding of PECD in the higher photon energy
region was explained by a different mechanism,
indicating the significance of the energy-dependence
to understand PECD. In this research project, we haveplanned to measure PECD in a wide photon energy
region to establish an effective model to describe thephysical origin of PECD.
We conducted the measurement of PECD at BL1U
with a velocity-mapping photoelectron imaging
detector [1]. Since this was our first experimental
action, detection efficiency and energy- and angularresolution were carefully inspected based on thecomparison with the literature results of typical PECD
systems: camphor and methyl-oxirane. Undulator
radiation was used to ionize the vapor sample, which
was introduced into the vacuum chamber as aneffusive beam. Photon energy was varied in the 10 - 20
eV region, which generated photoelectrons with the
kinetic energy of 0 - 8 eV. A set of PECD dataconsisted of the scattering images with circularly
polarized radiation. The controllability of thepolarization and the photon energy in the BL1U
undulator was quite useful for obtaining the difference
image data between the right/left-handed circularly
polarized radiations under the constant measurement
conditions.
Our measurements well reproduced the PECD
images of camphor and methyl-oxirane in the previous
studies. Examples of the observed results of camphor
are shown in Fig. 1. The forward-backward
asymmetry with respect to the light propagation
direction (vertical in Fig. 1), which is experimental
evidence of PECD, exhibited opposite signs for l- andd-camphor enantiomers. The radial distributions
indicating the state-specific PECD showed a good
agreement with the previous measurements. The
photon energy dependence of the PECD images was
also confirmed in this measurement (Fig. 1). Further
analysis was limited at present by a relatively large
photon energy width (ΔE/E ≈10 %), which smears
PECD due to overlapping of the photoelectron bands.
Feasibility of the PECD measurements with BL1U
was positively demonstrated in the present study. We
found possible modifications to BL1U to improve thequality of the PECD data.

Fig. 1. Photoelectron circular dichroism of l- and dcamphor enantiomers measured at BL1U. (a) and (c);d-camphor, (b) and (d); l-camphor. Photon energydependence is shown as the difference between theimage data with hν= 120 nm ((a) and (b)) and hν= 60
nm ((c) and (d)).
[1] T.Kaneyasu et al., Phys. Rev. A 95 (2017) 023413.

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BL1B, BL6B
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, T. Yamada2, K. Tanaka3 and F. Teshima3

International Research Center for Elements Science, Institute for Chemical Research, Kyoto University,
Uji 611-0011, Japan
2
Faculty of Science and Engineering, Keio University, Yokohama 223-8522, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, JapanTHz and Low-frequency region spectroscopic
analysis was performed on various organic compounds
to investigate the dynamic behavior of organic
molecules under microwave irradiation.
Microwave-enhanced chemical process has been
recently focused intensely because the high-speed andhigh-selective molecular conversion provide a highly
efficient chemical process which never accessible byusing the conventional heating techniques such as oilbath and electric heater. Prof. Yamada and hiscolleagues found that axially chiral biaryl compounds
such as 1-methyl-6H-naphtho[2,1-c]chromen-6-one 1
show microwave-enhanced racemization behavior
under the irradiation of 2.45 GHz microwave, where
the corresponding enantiomerically pure atropisomer
efficiently undergoes racemization through therotation around the biaryl axial linkage [1]. Theoreticalsimulation demonstrated that the rotation-induced
atropisomerism closely corresponds to molecular
dynamics coupled with THz to low-frequency
vibration modes (5–800 cm-1). We considered thatmicrowave irradiation could excite the internalrotation through such vibration modes and themolecular dynamics under microwave irradiation canbe detected by THz and low-frequency region
vibration spectroscopy. For this reason, we examined
the THz-low frequency spectroscopic analysis ofvarious biaryl organic compounds including 1.
All the samples of biaryl compounds were once
dissolved into the appropriate solvents such as CH2Cl2
and THF and directly dropped onto a THz-transparent
diamond window to set the sample stem which insets
into the vacuum chamber. The THz-low-frequency
measurement carried out under the standard conditionof the beamline using HDL-5 Infrared Laboratories I.R
detector bolometer in the range of 30–130 and 130–680
cm-1 with appropriate beam splitters of Mylar and
KBr/Ge, respectively. The resulting raw spectrum wasprocessed by dividing the reference spectrum of
diamond plate for baseline correction. Theoreticalsimulation of the spectrum was performed by DFT at
M06-2x/6-311G+(d,p) level of theory using vibrationalfrequency scale factor for this level (0.967) [2]. The
spectrum of compound 1 is shown in Fig. 1. with thecorresponding DFT-simulated spectrum where thespectrum in the Mid-infrared range from 350–680 isqualitatively agreed with the real specrum.
[1] S. Tashima, K. Nushiro, K. Saito and T. Yamada,
Bull. Chem. Soc. Jpn. 89 (2016) 833.
[2] Computational Chemistry Comparison andBenchmark DataBase (CCC BDB),
https://cccbdb.nist.gov/vibscalejust.asp

Fig. 1. Low-Frequency IR Spectrum of 1: Experimental (red solid line) and DFT-simulated with smearing(blak solid line).

108
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Ⅲ -3. Chemistry

BL3U

π-π Interactions Between Liquid-Crystal Molecules Studied by in-situ X-ray
Absorption Spectroscopy
2

H. Iwayama1, 2 and M. Nagasaka1, 2

Editorial Board, 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
1

The liquid crystal is one of the most importantmaterials for display devices. In the case of nematic
liquid crystals, the rod-shaped organic molecules haveno position order, but they self-align to have longrange directional order with their long axes roughly
parallel. Since X-ray absorption spectroscopy (XAS)
is sensitive to a local atomic geometry and thechemical state of the atom of one specific element,
XAS spectroscopy is suitable to investigate structuresof liquid crystals materials. However, XAS
measurement of liquid-crystal materials is limited to
one in a solid phase due to the requirement of highvacuums of a sample chamber. Considering the factthat they work as display device in a liquid-crystal
phase, we need to measure XAS in a liquid-crystal
phase. Recently, our colleague, Nagasaka developed aliquid cell, which allows us to measure XAS spectra ofliquid samples [1]. In our work, we measure XAS ofliquid-crystal materials in the liquid-crystal phase.
Our sample is 4-Cyano-4’-pentylbiphenyl (5cb),
which is one of the most popular liquid-crystal
materials. A schematic draw of 5cb molecules isshown in Fig. 1. The phase transition temperature ofliquid to liquid-crystal and liquid-crystal to solid are
35 and 22.5 °C, respectively. The XAS measurements
were carried out at UVSOR BL3U. After liquid-crystal
cell which is composed of two Si3N4 membranes wasfilled with the liquid-crystal sample, the thickness ofliquid-crystal sample was optimized by controlling the
He gas pressure around the cell. The photon energy
was calibrated by using the C-K edge XAS spectrumof the proline thin layer.
Figure 2 shows a C K-edge XAS spectrum of 5cb
sample at 26 °C, which correspond to the liquid-crystal
phase. We observed several peaks and a strong peak at
285 eV. To understand XAS spectrum and perform apeak assignment, we need theoretical calculation. We
introduced a quantum chemical calculation software,
StoBe, which is based on the density functional theory
and can calculate core hole states. A calculated
spectrum is also shown in Fig. 2 and reproduces
experimental results well. By analyzing the calculation,
it is revealed that the strong peak at 285 eV correspondto a core excitation of C 1s to π* orbitals of phenylgroup.
Figure 3 shows peaks at 285 eV for each phase. We
observed high energy shift of the peak at the phasetransition between solid and liquid-crystal phases.
This phase dependence of core excitations reflects thechange of molecular alignments between each phase.

Our results show the phase transition between solid toliquid-crystal phases weaken π-π interaction between
molecules.

Fig. 1 Schematic draw of 4=Cyano-4’- pentylbiphenl(5cb) molecules.

Ⅲ-3

Fig. 2 Experimental and calculated C K-edge spectraof 5cb molecules. Experimental spectra were measured
at 26 °C (liquid-crystal phase).

Fig. 3 C K-edge XAFS spectra of 5cb molecules at 18(solid), 26 (liquid-crystal) and 39 °C (liquid).
[1] M. Nagasaka, H. Yuzawa and N. Kosugi, J. pectrosc.
Relat. Phenom. 200 (2015) 293.

109
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Ⅲ -3. Chemistry

BL3U

Oxygen K-edge X-ray Absorption Spectroscopy of Aqueous Acetonitrile
Solution at Different Concentrations
2

Ⅲ-3

M. Nagasaka1,2, 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

Aqueousacetonitrile
solutionshows
microheterogeneity, where two liquids seem to bemixed in a macroscopic scale but are inhomogeneousin microscopic scale [1]. Soft X-ray absorption
spectroscopy (XAS) is an effective method toinvestigate molecular interactions of aqueous
acetonitrile solutions since molecular interactions ofacetonitrile can be revealed by the C and N K-edge,
and the interaction of solvent water molecules isseparately revealed by the O K-edge. Recently, several
groups measured O K-edge XAS of aqueous
acetonitrile solutions. By increasing the molar fractionof acetonitrile, the main-edge peak (538 eV) becomes
sharper in profile, which means that isolated watermolecules exist in aqueous solutions [2]. However,their studies reported molecular interaction of solvent
water only in a limited concentration region. In thisstudy, we have investigated molecular interactions ofsolvent water in the wide concentration regions byusing O K-edge XAS [3].
The experiments were performed at soft X-ray
beamline BL3U. XAS spectra of liquid samples were
measured by a transmission-type liquid flow cell [4].
Figure 1(a) shows O K-edge XAS spectra ofaqueous acetonitrile solutions (CH3CN)x(H2O)1−x at
different concentrations from x = 0.0 to 0.9 by 0.05
step. By increasing the molar fraction of acetonitrile(x), the pre-edge peaks (535 eV) related to the 4a1
states show lower energy shifts and the main-edge
peaks related to the 2b2 states show sharper profile.
The sharp profile in the main-edge peak is caused bydecreasing molecular interactions among watermolecules. This sharp profile starts to grow above x =0.2, which means that water molecules form the dipole(DP) structure with acetonitrile at x > 0.2.
Figure 1(b) shows the energy shifts of the pre-edge
peaks at different concentrations from those of liquidwater (x = 0.0). The larger energy shift at higher molar
fraction of acetonitrile is caused by the formation of an
isolated water molecule enclosed in liquid acetonitrile
as shown in the inset. The concentration-dependent
energy shift is gentle at 0.7 > x but is larger at x > 0.7.
It suggests that the population of isolated watermolecules embedded in liquid acetonitrile is rapidly
increased at x > 0.7.
We have also measured C and N K-edge XAS ofaqueousacetonitrile
solutionatdifferent
concentrations for studying molecular interaction ofacetonitrile in aqueous solution [3]. In the middle
concentration region, the acetonitrile clusters are fully

surrounded by water with the DP interactions, whichis the key structures to emerge the microheterogeneity.
The energy shifts of the pre-edge peaks in O K-edge
XAS also confirm the DP interactions between
acetonitrile and water, which forms isolated watermolecules in acetonitrile-rich regions.

Fig. 1. (a) O K-edge XAS spectra of aqueous
acetonitrile solution at different concentrations. The
pre-edge and main-edge peaks are changed to thedirection of arrows by increasing the molar fraction ofacetonitrile (x). (b) Energy shifts of the pre-edge peaks
at different concentration from those of liquid water (x= 0.0). The inset shows a water molecule enclosed in
two acetonitrile molecules.
[1] Y. Marcus, J. Phys. Org. Chem. 25 (2012) 1072.
[2] N. Huang et al., J. Chem. Phys. 135 (2011) 164509.
[3] M. Nagasaka, H. Yuzawa and N. Kosugi, J. Phys.
Chem. B 124 (2020) 1259.
[4] M. Nagasaka et al., J. Electron Specrosc. Relat.
Phenom. 224 (2018) 93.

110
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Ⅲ -3. Chemistry

BL3U

Hydrated Water Structure of N,N-Dimethylglycine Studied by Soft X-Ray
Absorption Spectroscopy
N. Fukuda1, S. Ohsawa1, H. Yuzawa2, M. Nagasaka2,3 and K. Okada1

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
1

Living cells protect themselves from external stresssuch as hydrostatic pressure and drought by regulating
the amount of solutes called osmolytes [1]. Several
organic osmolytes have a characteristic feature of theform as a zwitterion. Found most commonly in cells
are fully N-substituted amino acids, although partiallyand non-substituted amino acids also take azwitterionic form. Glycine betaine (also known as
N,N,N-trimethylglycine or TMG) is among the mostcommon species in cells, and its amount dominates
much over N-methylglycine (NMG) and N,Ndimethylglycine (DMG). Many recent studies haverevealed that the higher-order structure of proteins isprotected through the indirect interaction between thehydrated proteins and osmolytes. Studying thedifference in hydration structure between TMG and
DMG gives a clue to understand why biologicalsystems prefer fully N-substituted amino acids overpartially substituted counterparts. The hydration of
DMG has not yet investigated in this sense. We
therefore focus in this report on the electronic structureof the hydrated water molecules of DMG comparedwith that of TMG by soft X-ray spectroscopy.
Photoabsorption spectra at the oxygen K-edge were
measured in the transmission mode at room
temperature. Aqueous solutions of DMG and TMG
with concentrations up to 1.0 M were introduced bymeans of a tubing pump into a liquid flow cell [2]installed on the soft X-ray beamline BL3U. The flow
cell for this study was equipped with a pair of windows
made of thin silicon nitride membrane. The incident
photon energy was calibrated to the peak at 530.88 eVof a polymer film [3].
Figure 1 shows the O 1s absorption spectra of liquidwater, DMG and TMG aqueous solutions enlarged at
the water 4a1 resonance band. The peak top at 534.6
eV is shifted by +0.20 and −0.05 eV for DMG and
TMG solutions, respectively. The apparent shiftobserved for the TMG solution is consistent with ourprevious measurement [4]. The hydration structure is
extracted by deconvolution of the band consisting of
the hydrated and bulk water components thanks to thechemical shift present in the inner-shell excitation ofmolecules under different chemical environments. The
second and fourth derivatives (not shown) of theabsorption spectra of liquid water suggest that there
exist two components in the 4a1 resonance band. The
derivatives for the DMG and TMG solutions indicatethat additional components are necessary to reproduce

the spectra. The latter components can be ascribed tothe hydrated water acting as a hydrogen-bond donor or
acceptor to interact with the solutes. The validity of thepresent analysis is supported by the fact that the areaof the components increases with the concentration.
The apparent blue shift for the DMG solution isreasonably explained by the presence of the hydrated
water acting as a hydrogen-bond acceptor. Because its
component is placed at the higher energy side of theband, the intensity around it is higher than that ofliquid water and of the TMG solution. A further
analysis is in progress and the results will be publishedelsewhere.

Fig. 1. Enlarged O 1s photoabsorption spectra of liquidwater, 1.0-M DMG and 1.0-M TMG aqueous solutionsin the 533–536 eV region.
[1] P. H. Yancey, M. E. Clark, S. C. Hand, R. D. Bowlus
and G. N. Somero, Science 217 (1982) 1214.
[2] M. Nagasaka, T. Hatsui, T. Horigome, Y. Hamamura
and N. Kosugi, J. Elec. Spectrosc. Relat. Phenom. 177(2010) 130.
[3] M. Nagasaka, H. Yuzawa, T. Horigome and N.
Kosugi, J. Elec. Spectrosc. Relat. Phenom. 224 (2018) 93.
[4] S. Ohsawa, N. Fukuda, H. Iwayama, H. Yuzawa, M.
Nagasaka and K. Okada, UVSOR Activity Report 201846 (2019) 115.

111
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Ⅲ -3. Chemistry

BL3U

X-ray Absorption Measurements Applied to Aqueous Solutions ofCarboxylate Ions, in the Vicinity of the O K-edge Ionization Thresholds
D. Céolin1, T. Saisopa2, K. Klaiphet2, J. Borsup2, P. Songsiriritthigul2, H. Yuzawa3
and N. Kosugi4

2

Ⅲ-3

1
Synchrotron SOLEIL, L'Orme des Merisiers Saint-Aubin BP 48 91192 Gif-sur-Yvette Cedex, France
Research Network NANOTECH-SUT on Advanced Nanomaterials and Characterization and School of Physics,
Suranaree University of Technology, Nakhon Ratchasima 30000, Thailand
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
4
Institute of Materials Structure Science, KEK, Tsukuba 305-0801, Japan

It is well established in organic chemistry that thereactivity of a specific group can be predictedconsidering several additive or competing effects
influenced by the energy position and occupation of
the frontier orbitals. In this context, it is interesting toevaluate the role of the molecular skeleton on which acarboxylate group is fixed (R in R−COO-), and how its
inductive or mesomeric properties might influence thereactivity of the system.
One method to determine the energy position of theunoccupied orbitals of carboxylate is to perform XAS
measurements. This was done for instance on aqueous
solutions of acetate salts – with the motivation to probe
the pairing efficiency of −COO- with different types of
positive ions [1].
At the beamline BL3U, and using the liquid cell intransmission mode, we measured XAS in the vicinity of
the O K-edge ionization threshold on sodium formate,acetate, propionate, trifluoroacetate and benzoate (R =H, CH3, C2H5, CF3 and C6H5 respectively). See Fig. 1(C2H5 spectrum is not shown but the resonances
position is similar to those of CH3).
The resonance located at hν = 535 eV is attributed to
the O1s excitation of water to its first empty orbital. The
O1s  π*CO resonances associated with the −COOgroup are located between 531.5 eV and 533.5 eV, andthe small structure at 530.9 eV is due to surface
oxidation of Si3N4 membranes. To give a preliminaryinterpretation of these results, we looked at theinductive and mesomeric properties of R. With R = H
taken as a neutral reference, CF3 and C6H5 are electron
withdrawing groups (-I), and CH3 and C2H5 are electron
donating groups (+I). CF3 withdraws electrons becauseof the very strong electronegativity of the fluorine atoms.
C6H5 is also generally considered as -I compared withhydrogen due to the sp2 hybridization of the carbon
atom of the phenyl ring bonded to −COO-. On thecontrary, for CH3 and C2H5, the carbon bonded to thecarboxylate has a sp3 hybridization and is considered aselectron donating. The sp2 hybridized orbitals have alarger s-character than the sp3 ones, and contrary to the
2p-electrons, the 2s-electrons have the property to be
more tighten to the nucleus. This leads to less diffuse sp2
hybridized orbitals and to an increase of theirelectronegativity. To explain the strong shift of the C6H5
group, one can invoke its mesomeric property (see Fig.

2). Despite more complex and probably weaker, asimilar effect might be considered for CF3 as well due
to possible hyperconjugation process [2].
All effects taken into account, it seems that the total
charge density located in the vicinity of the oxygens of
the carboxylate group plays a crucial role on theresonances position. Induction has an influence on theσ-skeleton of the molecule, and thus might modify thespatial extension of the oxygen lone-pairs carried by−COO-, and electron delocalization through the πsystem clearly increases the negative charge on theoxygen of carboxylate. These hypotheses need to be
confirmed, and their relation with the resonances
position will be the subject of theoretical investigations.

Fig. 1. X-ray absorption spectra of 1 M aqueous
solutions of sodium formate, acetate, propionate,trifluoroacetate and benzoate, in the vicinity of the O
K-edge ionization thresholds. Normalization is doneon the peak maximum at 535 eV.

Fig. 2. Resonating forms of benzoate.
[1] J. S. Uejio et al., PNAS 105 (2008) 6809, E. F. Azizet al., J. Phys. Chem. B 112 (2008) 12567, T. Petit etal., Structural Dynamics 1 (2014) 034901.
[2] L. M. Stock, M. R. Wasielewski, Progress inPhysical Organic Chemistry 13, chapter 4 (John Wiley& Sons, Inc., 1981).

112
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BL3U

NEXAFS Study of μ-Nitrido-Bridged Iron Phthalocyanine Dimer with
Graphite Surface
1

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

Direct C-H activation of light alkanes such as
methane and ethane under mild reaction condition is
an important challenge in the field of catalytic
chemistry because efficient conversion of light alkanes
into valuable chemical raw materials can contribute to
reduce our dependence on petroleum resources. μNitrido-bridged iron phthalocyanine dimer (1 in Fig.
1) is one of the most potent molecule-based catalysts
for direct C-H activation of methane and ethane [1,2].
It can catalytically convert light alkanes into
corresponding alcohols, aldehydes, and carboxylic
acids in an acidic aqueous solution at a lower
temperature below than 100 °C in the presence of
H2O2. Recently, we found that the catalytic methane
oxidation activity of 1 was significantly enhanced byadsorption on graphite surface. In order to clarify themechanism of this enhancement, we investigated thestructure of 1 on graphite surface, as well as theinteraction between 1 and graphite by XAFS study.
1 was adsorbed on a highly oriented pyrolytic
graphite (HOPG) to prepare 1/HOPG as shown in Fig.
1. N K-edge NEXAFS measurements were performedat the soft X-ray beamline BL3U of UVSOR [3]. For
these measurements, 1/HOPG was fixed with doublesided conductive carbon tape onto a stainless sample
holder. The holder was fixed on a rotatable linear andinstalled into a vacuum chamber (< 1 × 10−5 Pa). The
N K-edge NEXAFS spectra were obtained in total
electron yields by measuring a sample drain current.
Figure 2 (a) shows a comparison of the NEXAFS
spectra obtained at three different incident angles (θ =90°, 55°, and 30° from the HOPG surface). The peaks
at around 398 eV are assignable to the excitation of N
1s core electrons to the C=N π* orbitals of thephthalocyanine. Considering that the C=N π*transition moment is perpendicular to the p-surface ofthe phthalocyanine, the high intensity of the π* peak at
θ = 30° implies that the π-surface was parallel to the
HOPG surface. Figure 2 (b) shows incident-angle
dependence of the C=N π* peak intensity at 398 eVwith the simulated curve calculated from the tilted
angle of the C=N π* transition moment from thenormal of the HOPG surface [4]. As a result of thefitting procedure, the tilted angle of the C=N π*transition moment is approximately 0 from the surface
normal. This indicates that the phthalocyanine πsurface was parallel to the HOPG surface as shown in
Fig. 1b.

Fig. 1. Adsorption of 1 on a HOPG substrate.

Ⅲ-3

Fig. 2. (a) Comparison of the NEXAFS spectra of
1/HOPG at three different incident angles (θ = 90°, 55°,
and 30°). (b) Dependence of the C=N π* peak intensity(398 eV) on the incident angle with the simulated
curve.
[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. M. 43 (2019)11477.
[3] T. Hatsui, E. Shigemasa and N. Kosugi, AIP Conf.
Proc. 705 (2004) 921.
[4] Y. L. Huang, W. Chen, S. Chen and A. T. S. Wee,
Appl. Phys. A. 95 (2009) 107.

113
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BL3U

Oxygen K-edge X-ray Absorption Spectroscopy of Aqueous Ethanol
Solution 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

Ⅲ-3

Aqueous ethanol (EtOH) solution is a model toexplore competition between hydrophilic (namely,
HB: hydrogen bond) and hydrophobic interactions andis important to understand several physical, chemical,
and biological phenomena [1]. Soft X-ray absorption
spectroscopy (XAS) is an effective method toinvestigate HB with water molecules [2]. Recently,
several groups measured O K-edge XAS of aqueous
EtOH solutions [3,4], but they reported spectra only ina limited concentration region. In this study, we haveinvestigated HB interaction between EtOH and waterin the wide concentration region by O K-edge XAS.
The experiments were performed at soft X-ray
beamline BL3U. XAS of liquid samples were
measured by a transmission-type liquid flow cell [5].
Liquid samples are exchanged in situ by using a tubing
pump without changing the sample position.
Figure 1(a) shows O K-edge XAS spectra ofaqueous EtOH solutions at different concentrations at
25 °C. In the XAS spectrum of liquid water (x = 0.0),
the pre-edge peak at 535 eV corresponds to thetransition of O 1s electron to an unoccupied 4a1 orbitaland reflects HB interaction between water molecules[2]. On the other hand, the pre-edge feature of liquid
EtOH (x = 1.0) is embedded in the main peak at 538
eV, as observed in the previous study [3, 4]. As
observed in the inset of Fig. 1(a), the pre-edge region
shows isosbestic points at 534.9 and 535.9 eV. It
indicates that the pre-edge region consists of two
spectral contributions from EtOH and water, which isalso suggested by the previous study [3].
Figure 1(b) shows spectral fractions of EtOH andwater in the pre-edge region at different molar factionsof EtOH (x) obtained by fitting the superposition of pure
EtOH (x = 1.0) and pure water (x = 0.0). The spectral
fraction of water is decreased and that of EtOH isincreased by increasing the molar fraction of EtOH (x).
However, these changes show nonlinear features, where
the changes of EtOH is crossed with that of water at x =0.65. It is a different trend from O K-edge XAS ofaqueous methanol (MeOH) solutions, where thespectral fraction of MeOH is changed linearly and iscrossed at x = 0.5 [6]. Since the ethyl group is larger thanthe methyl group, the HB interaction between watermolecules would be increased by the strongerhydrophobic interaction in EtOH than in MeOH,
resulting the higher ratio of water spectral fraction at the
EtOH-rich concentration region.
In the future, we will discuss hydrophobic interactionsof the ethyl group in EtOH more directly from the C Kedge XAS spectra.

Fig. 1. (a) O K-edge XAS spectra of aqueous EtOH
solutions at different concentrations from x = 0.0 to 1.0
by 0.05 step. The inset shows the expansion of the preedge region. (b) Spectral fractions of EtOH and water inthe pre-edge region as a function of the molar fractionof EtOH (x) obtained by fitting the superposition of pure
EtOH (x = 1.0) and pure water (x = 0.0).
[1] A. Ghoufi et al., J. Phys. Chem. B 120 (2016) 793.
[2] J. W. Smith and R. J. Saykally, Chem. Rev. 117(2017) 13909.
[3]I. Juurinen et al., J. Phys. Chem. B 118 (2014) 8750.
[4] R. K. Lam et al., J. Chem. Phys. 144 (2016)
191103.
[5] M. Nagasaka et al., J. Electron Specrosc. Relat.
Phenom. 224 (2018) 93.
[6] M. Nagasaka et al., J. Phys. Chem. B 118 (2014)
4388.

114
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BL3U

Observations of Micelle Formation in Aqueous Organic Solutions
Using Soft X-ray Absorption Spectroscopy
J. J. Lin1, G. Michailoudi1, Kamal Raj R.1, H. Yuzawa2, M. Nagasaka3,4 and N. L. Prisle1

Nano and Molecular Systems research unit, University of Oulu, P.O. Box 3000,
90014 University of Oulu, Finland
2
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, 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

Changes in concentration and pH also affect the prepeak to main peak ratio. A large drop in absorption isobserved going from pH ~6 to pH ~5 for both sodium
hexanoate concentrations. At low pH values, theabsolute absorption values of 0.75 CMC solutions areroughly the same as the 3 CMC solutions. For the 3
CMC sodium hexanoate solutions, the main
absorption peak mostly disappears.
Additional analysis of the spectra is ongoing,
including comparison to previous measurements at
BL3U of similar organic compounds in aqueous
solution [4]. Detailed fitting of the spectra will be
carried out to identify the underlying absorption peaks.
Complementary measurements and theoreticalprediction for these systems are also in progress.
0.75 CMC Sodium hexanoate, PH= 7.00
0.75 CMC Sodium hexanoate, PH= 6.03
0.75 CMC Sodium hexanoate, PH= 4.69
0.75 CMC Sodium hexanoate, PH= 3.98

0.4

0.3
Intensity [abs. units]

Amphiphilic compounds in aqueous solutions are
known to self-assemble into structures known as
micelles above some critical micelle concentration(CMC). The role of amphiphiles in cloud droplet
nucleation is still debated, with the specific impact of
micelles unaccounted for in cloud formation models[1]. The uncertainties involving the formation of cloud
droplets from organic cloud nuclei are some of thelargest in the understanding of anthropogenic climate
forcing [2].
Aqueous solutions of sodium hexanoate werestudied using X-ray absorption spectroscopy (XAS) at
the BL3U beamline using the liquid flow cell setup.
The range of reported CMC values for sodium
hexanoate is 0.53–1.7 M [3]. A value of 0.9 M wasassumed and solutions at 0.75 and 3 times the CMC
value (i.e. 0.68 and 2.7 M) were made for this study.
For each concentration, the solutions were made at thepKa of hexanoic acid as well as one pH unit above andbelow the pKa.
The sensitivity of XAS to chemical environment
provides information about the bulk properties of theaqueous components. XAS measurements were madeat the carbon K-edge in order to specifically capture
the aliphatic R(CH)R’ and carboxylic C(=O)OH
carbon absorption peaks. The measured photon energy
range was from 280 to 300 eV with resolution of 0.02
eV from 285 to 290 eV and 0.1 eV for the rest of theenergy range. Measurements were also made on purewater in the liquid cell in order to remove the carbon
signal from contamination in the beamline and theliquid cell. The energy of the incident X-rays wasregularly calibrated using XAS measurements on athin polymer film (ProLINE) which has a well-definedabsorption peak. The temperature of the liquid samples
was controlled to 25 C.
Measured absorption spectra are shown in Fig. 1.
Background absorption has been removed bysubtracting the pure water spectrum, and each
spectrum has been calibrated using the polymer film
spectra taken immediately before and after the sample
spectrum. For most of the spectra, a main peak isobserved at around 289 eV. In general, the absorptionof the sample decreases with increasing sodium
hexanoate concentration and decreasing pH value.

3 CMC Sodium hexanoate, PH= 6.03
3 CMC Sodium hexanoate, PH= 4.84
3 CMC Sodium hexanoate, PH= 3.81

0.2

0.1

0.0

-0.1
280

285

290

295

Photon energy [eV]Fig. 1. Preliminary absorption spectra for aqueous
sodium hexanoate solutions at 0.75 and 3 times thecritical micelle concentration and for various pH values.
[1] N. L. Prisle et al., Atmos. Chem. Phys. 10 (2010)5663.
[2] O. Boucher et al., Clouds and Aerosols. In: Climate
Change 2013: The Physical Science Basis. Contributionof Working Group I to the Fifth Assessment Report of theIntergovernmental Panel on Climate Change (Cambridge
University Press, Cambridge and New York City, 2013).
[3] P. Mukerjee and K. J. Mysels, Critical Micelle
Concentrations of Aqueous Surfactant Systems (U.S.
National Bureau of Standards, Washington, D.C.,
1972).
[4] J.J. Lin et al., in prep.

115
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Ⅲ -3. Chemistry

BL3B

Optical Investigation on Fluoro-olefins in VacuumUltraviolet for New Refrigerant Gas Development
K. Yamanoi1,2, Y. Sakata1, H. Iwayama3, Y. Hasumoto1,2, T. Takakuwa1,2, O. Yamamoto1,2
and M. Noumi1,2
1
Osaka university, Suita 565-0871, JapanDAIKIN Industries Ltd, Settsu 566-8585, Japan
3
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan2

Ⅲ-3

Chlorofluorocarbon (CFC), hydrochlorofluorocarbon (HCFC), and hydrofluorocarbon (HFC) havebeen used as a refrigerant. These gases have highglobal warming potential (GWP) over 100. Recently,
the hydrofluoroolefin (HFO) gases are expected as
new low environmental load refrigerant due to its low
GWPs since olefin gas is unstable and easily
decompose by ultraviolet light in nature. In order toput HFO into practical use as a refrigerant, it isnecessary to clarify the physical characteristics of
HFO such as UV absorption and decomposition
process. In this study, we measured the vacuum
ultraviolet (VUV) absorption and fluorescence oftetrafluoroethylene (TFE). The absorption andfluorescence spectra measurements were carried out in
BL3B in UVSOR Synchrotron Facility. TFE gas wasfilled in the cell having MgF2 windows at 100 Pa. The
optical path length in the cell is 35 mm. The samplegas filled cell was placed in the vacuum chamber and
VUV light was irradiated through the MgF2 windows
and detected by a photodiode. The photoluminescence
was measured by the spectrometer at 90 degree fromincident beam. Figure 1 shows the photograph of thesample cell and schematics of the experimental setup.
Figure 2 shows the transmission spectra of TFE at
100 Pa. We could clearly observed the absorption atabout 145 nm and 190 nm. The absorption at 145 nm
is attributed to the stretching and twisting of carbon
double band and the 190 nm is the transition from π to
π*, respectively [1].
Figure 3 shows the photoluminescence spectra of
TFE at 100 Pa excited by 145 nm. The broad
fluorescence from 250 to 350 nm with 276-nm peak was
observed. This emission is CF2 singlet transition [2].
In conclusion, we could observe the opticalproperties of TFE in VUV region. The results let us
know the possibility of the UV- or VUV-induced
decomposition dynamics of fluoro-olefins using
optical technique such as pump and probe method.

Fig. 1. Photograph of the sample cell and schematicsof the experimental setup.

Fig. 2. Transmission spectra of TFE.

Fig. 3. Photoluminescence spectra of TFE.
[1] G. Belange et al., J. Chem. Phy 55 (1971) 2055.
[2] B. A. Williams et al., Chem. Phy. Let. 309 (1999) 75.

116
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Ⅲ -3. Chemistry

BL4B

Electron Coincidence Spectroscopy for Poly(Methylmethacrylate)Thin Film
2

Y. Hikosaka1 and S. Wada2

Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
Department of Physical Science, Hiroshima University, Higashi-Hiroshima 739-8526, Japan
1

Irradiation of soft x-ray to an organic thin film maylead a core electron ejection from a specific atom in themolecular constituent. The core hole thus generated
decays mainly by emitting an Auger electron. The
spectrum of the Auger electron contains useful
information of the valence orbitals relevant to the decay
process. In case that the constituent molecule contains
the same element at different sites, Auger structuresassociated with these core holes overlap each other inthe conventional Auger spectrum. The atomic sitewhere the core hole has been formed can be identified
by the chemical shift of the photoelectron ejected on the
core-hole creation. Accordingly, Auger structuresassociated with individual core holes can be filtered out
by coincidence observations with chemical-shifted
photoelectrons. Such photoelectron-Auger electron
coincidence spectroscopy can be performed with highefficiency by using a magnetic bottle electron
spectrometer [1]. The adaptability of the spectrometerto solid samples is already verified [2].
In this study, photoelectron-Auger electron
coincidence measurements were made for poly(methyl
methacrylate) (PMMA) thin films on a copper wire. The
magnetic bottle electron spectrometer employed in thisstudy is equipped with an electrostatic retarder [3], to
improve the energy resolving power. PMMA has carbon
atoms in different chemical environments within asingle unit (see inset of Fig. 1). Figure 1 shows a C1s
photoelectron spectrum of PMMA measured at a photon
energy of 482.4 eV. At least three photoelectron peaks
are identified in the spectrum, and their assignments areindicated with labels of the same colors as used in thechemical formula (inset). The Auger spectra observed incoincidence with the photoelectrons for these threepeaks are plotted in Fig. 2, where the colors of thespectra follow those allocated in Fig. 1. Tangible
differences in spectral feature are identified among thecoincidence Auger spectra. Calculation is under way, tointerpret the spectral features.

[1] J. H. D. Eland et al., Phys. Rev. Lett. 90 (2003)
053003.
[2] Y. Hikosaka et al., J. El. Spectrosc. Rel. Phenom.
213 (2016) 17.
[3] Y. Hikosaka et al., J. El. Spectrosc. Rel. Phenom.
192 (2014) 69.

Ⅲ-3
Fig. 1. C1s photoelectron spectrum of PMMA
measured at a photon energy of 482.4 eV.

Fig. 2. Auger spectra observed in coincidence with
C1s photoelectrons.

117
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Ⅲ -3. Chemistry

BL5B

Evaluation of Polarization Characteristic of Monochromatized Synchrotron
Radiation by Observing Zeeman Quantum Beat
1

Ⅲ-3

Y. Hikosaka1, H. Iwayama2 and T. Kaneyasu3

Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
2
Institute for Molecular Science, Okazaki 444-8585, Japan
3
SAGA Light Source, Tosu 841-0005, Japan

Evaluation of the polarization characteristic ofmonochromatized synchrotron radiation is an importantconcern in synchrotron radiation researches. The opticalcomponents of monochromators and beamlines modify
the original polarization state of the synchrotron
radiation. The effect of the modification is pronounced
in the extreme ultraviolet (XUV) range, as steeper
incidence angles to the optical elements are usuallyadopted for the monochromatization. The diagnosis of
the polarization state of XUV light can be preciously
made with an optical method using polarimeters. Sucha measurement, however, requires stringent alignmentsof the polarimeters, and the fabrication andmanipulation of an effective polarimeter system are stillchallenging. Over the optical method, observation of amaterial process responding to light polarization has anadvantage in easy measurement. Angler distribution ofphotoelectrons emitted from gas samples has been
conveniently utilized for evaluating the polarization.
Here we propose that the polarization characteristicof monochromatized synchrotron radiation in the XUVrange can be evaluated by observing quantum beat of
Zeeman-split Rydberg states in He [1]. A fluorescencedecay curve measured at the He 1s→6p excitationenergy is presented in Fig. 1 (black dots), where UV
fluorescence photons emitted on the 6p→2s decay isdetected by a photomultiplier. The photomultiplier wasplaced at right angles to both the polarization andpropagation of the monochromatized synchrotron light,
and a magnetic field of 21.1 mT was applied along thelight propagation axis.
The fluorescence decay curve exhibits a quantum
beat oscillation superposing on the exponential-decay
form. This observation manifests the coherent
excitation to the Zeeman-split Mj=±1 levels. The
decay curve can be fitted with the formulaI(t) ~ [1 + PcosΔωt] exp(-γt)(1)
where P, Δω, and γ are the polarization degree, thetransition frequency of the initial excitation, and thelifetime of the excited state, respectively. Thisequation indicates that visibility of the oscillation
superposing on the exponential decay reflects directly
the degree of the light polarization. The solid red curvein Fig. 1 is the best fit to the observation, where thetemporal resolution of the measurement was assumed
as the Gauss function of 2.9 ns FWHM. The fitting
indicates the degree of the linear polarization to be
P=0.60±0.05. The polarization degree may be too poor,
even as the light provided by the bending magnet

beamline of the large acceptance in the verticaldirection. It is practically anticipated that the fitting
result underestimates the actual polarization degree.
This is because the fitting does not take into accountthe large detection solid angle for the present
fluorescence observation, while the phase of thequantum beat varies according to the detection angle
and the overlap of the quantum beats with different
phases in the detection solid angle reduces thevisibility of the observed quantum beat oscillation.
More accurate estimation of the polarization degree
can be achieved by observing fluorescence with asmaller detection solid angle, which is fully feasible
considering the favorable count rates in the present
investigation.

Fig. 1. Fluorescence decay curve (dots) of the 1s6p
excited state in helium, measured with a magnetic fieldof 21.1 mT. It was obtained by an accumulation around
10 min. The red solid curve is the best fit to theobservation (see text).

[1] Y. Hikosaka et al., submitted.

118
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Ⅲ -3. Chemistry

BL5B

Visible Fluorescence Studies on the Inner-shell Excitations in Kr and Xe
T. Kaneyasu1,2, Y. Hikosaka3, M. Fujimoto2,4 and H. Iwayama2,4

SAGA Light Source, Tosu 841-0005, Japan
Institute for Molecular Science, Okazaki 444-8585, Japan
3
Institute of Liberal Arts and Sciences, University of Toyama, Toyama 930-0194, Japan
4
The Graduate University for Advanced Studies, SOKENDAI, Okazaki 444-8585, Japan
1

2

The inner-shell excitations of atoms and molecules
have been studied in detail along with the developmentof synchrotron light sources and beamline techniques.
Usually the excitation spectra are obtained by detecting
the charged particles emitted in the energy relaxation
process following the inner-shell excitation. In
particular, the ion yield spectroscopy allows one toobtain excitation spectrum which is normally equivalent
to the photoabsorption.
We report on visible fluorescence studies on the Kr
3d and Xe 4d excitations. The visible fluorescencephotons are emitted in decays of the singly charged
ionic states formed by spectator Auger decay of theinner-shell excited state. We show that the fluorescence
yield is enhanced at a particular excited state, dependent
on the wavelength of the visible fluorescence.
Figures 1 and 2 show the Kr 3d and Xe 4d excitation
spectra obtained by the ion and fluorescence yield
spectroscopies. The visible fluorescence photons weredetected by a photomultiplier tube equipped with abandpass filter. The assignments of the peaks areindicated in the top panels. It is obvious that the peakstructures corresponding to the inner-shell excitations
appear more clearly in the fluorescence spectra. This isa consequence of the selective detection of the Auger
final states which cannot be populated via valence
ionization or normal Auger decay following the innershell ionization.
When the wavelength of the fluorescence photon is
selected by the bandpass filter, the spectral shapes
drastically change. In the Kr 3d excitations, while the
3d-15/25p state is enhanced when the 460-nmwavelength photons are detected, the intensity of the
3d-13/25p becomes large in the 450-nm-wavelength
spectrum. This spectral feature agrees with the previous
measurement [1], and is qualitatively explained by thespectator Auger decay from a specific initial state to a
specific final state. Similar behavior is observed in theXe 4d excitations as in Fig. 2. The measurement
approach presented here can be used to investigate thecascade decay following the inner-shell excitation [2].
Additionally, such a detection scheme will allow us toselectively observe the inner-shell excitations even withthe use of nonmonochromatized radiation.

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Fig. 1. Total ion yield (TIY), total visible fluorescence
yield (TFY) and wavelength-selected fluorescence
spectra in the Kr 3d excitation regime.

Fig. 2. Total ion yield (TIY), total visible fluorescence
yield (TFY) and wavelength selected fluorescence
spectra in the Xe 4d excitation regime.
[1] A. Sankari et al., Phys. Rev. A 77 (2008) 032720.
[2] R. Flesch et al., Phys. Rev. A 61 (2000) 062504.

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Ⅲ -3. Chemistry

BL6B

Cancelation of Orbital Degeneracy in Me4N[Pt(dmit)2]2
Graduate School of Science and Technology, Ehime University, Matsuyama 790-8577, Japan.
Geodynamics Research Center, Advanced Research Unit for High-Pressure, and Research Unit forSuperconductivity, Ehime University, Matsuyama 790-8577, Japan.
3
RIKEN, Wako 351-0198, Japan.
4
UVSOR Synchrotron Facility, Institute for Molecular Science, Okazaki 444-8585, Japan
1

2

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T. Yamamoto1,2,3, K. Takasugi1, T. Naito1,2, T. Teshima4, K. Tanaka4,
M. Nomura3 and R. Kato3

Orbital degrees of freedom and Jahn-Teller effect in
the inorganic and organic complex compounds havebeen investigated by chemists and physicist. Orbital
degeneracy in metal-dithiolene complexes has attracted
a growing interest since the discoveries of the singlecomponent metal and the photoconductivity. However,
only a few efforts have been devoted to revealing theorbital degrees of freedom. We have focused on
X[Pt(dmit)2]2 (dmit = 1,3-dithiole-2-thione-4,5-dithiolate
and X = monovalent cation) as a candidate of orbital
degeneracy. In the past study performed at BL6B andInstrumental center, we revealed that thedisproportionation reaction of the X = Me4Sb and Me4P
salts was ascribed to the cancelation of the orbital
degeneracy [1]. However, the behavior of the C=C
stretching modes of the X = Me4Sb salt was not always
identical to that of the X = Me4P salt although the crystal
structures were isostructural to each other. This result
suggested that the inter–molecular interaction depends
on the size of counter cation. We moved our focus on
the X = Me4N salt because the cation size is the smallest
among three compounds and the transfer integral in a
dimer is the smallest. In the present study at BL6B, weanalyzed the behavior of the C=C stretching modes in
the X = Me4N salt.
Figure 1 shows the infrared spectra obtained by thetransmission method. The B mode in the high–temperature phase was changed into the B1 and B2
modes in the low–temperature phase. The C mode waschanged into the C1 and C2 modes. The assignments ofthese vibrational modes are identical to those of the X =Me4Sb and Me4P salts [1]. The B and C modes belong
to [Pt(dmit)2]2-1. The B1 and C1 modes belong to thecharge–rich dimer ([Pt(dmit)2]2-1-Δ), and the B2 and C2
modes belong to the charge–poor dimer ([Pt(dmit)2]21+Δ). This temperature dependence is the evidence forthe disproportionation reaction. Similar to the previous
results on the X = Me4Sb and Me4P salts, the orbital
degeneracy at the high–temperature phase of the X =Me4N salt was canceled in the low–temperature phase.
The intensities of the A1 and A2 modes wereinversely proportional to the temperature, whichindicates that the A1 mode is assgined to one of the C=C
stretching modes of a charge–rich dimer. On the other
hand, the A1 mode of the X = Me4Sb salt was negligible
in the transmission spectra [1]. The intensity of the X =Me4P salt was smaller and larger than those of the X =Me4N and Me4Sb salts, respectively [1]. Therefore, theA1 mode belong to the symmetric vibration. Owing to
the asymmetric deformation in the charge–rich dimer,
the mutual exclusion rule cannot be exactly applicable
to both IR and Raman spectra. The difference in theintensities of the A1 modes among three compounds
suggests that the degree of deformation of the X = Me4N
salt is larger than those of the X = Me4N and Me4Sb salts.
This result indicates that the molecular deformation
suppresses the instability of the highest occupied orbital
arising from the decrease in the transfer integral in the
charge–rich dimer.

Fig. 1. Transmission spectra of Me4N[Pd(dmit)2]2.

[1] T. Yamamoto et al., UVSOR Acrtivity Report 201846 (2019) 126.

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