BL practice

BL17SU : Selective Observation of Molecules in Solution Under Ambient Condition by
Means of Soft X-ray Emission Spectroscopy
Takashi Tokushima and Masaki Oura (RIKEN/SPring-8)
1. Introduction
Knowledge of an electronic structure is quite important for understanding the properties ofmaterials. Especially, valence electrons play important roles in electric, magnetic and chemicalproperties. Valence orbitals/bands of gaseous/solid materials have been commonly investigated bymeans of photoemission spectroscopy (PES). However, an ordinary PES is unsuited for studying theelectronic structure of liquid materials since PES is a photon-in electron-out experiment which
detects photoelectrons in vacuum. Therefore, the soft x-ray emission (SXE) spectroscopy [1], whichis photon-in photon-out experiment observing valence electronic structure through energy spectra ofemitted photons, has been applied as an alternative method applicable to liquid samples. Since thefirst observation of SXE for liquid water 2002[2], liquids and solutions has been actively studied
using SXE spectroscopy in recent years [3-17].
Fig.1 shows schematic energy diagrams of soft x-ray absorption and emission spectroscopy. Soft x-ray
absorption (SXA) spectroscopy [18] measures absorption coefficient of electron transition from core tounoccupied orbitals. Therefore, SXA provided information on unoccupied states. Since SXA process generate
unstable core hole in the system, subsequent relaxation processes occurs within core-hole lifetime (few fsec forlight element). One of the relaxation pathways is soft x-ray emission (SXE). SXE spectra reflect occupied

valence electronic states via electronic transitions between core and valence orbitals.
Molecular orbitalsof water~few fsec

Absorption

Emission

Energy2b2

Intensity= Density of states

4a 1-Unoccupied

Soft x-ray
absorption

Occupied

1b1
Soft x-rayemission

3a 1

Valenceayx-r
ftSo

1b2y )-ra ont x issi
fSoEm
(2a 1Core
1a 1

Fig. 1 Schematic energy diagrams of soft x-ray emission and absorption
spectroscopy. Relation between spectral feature and molecular orbitals of watermolecule is shown as an example.

1Fig.2A shows binding energy of core orbitals
electronbindingenergiesin"X-ray

Binding energy [eV]

up to 2200 eV (Data were taken from the table ofDataBooklet"[19]). Binding energy of a core orbital islargely different depending on elements. Corelevel

spectroscopies

have

thus

theuniquecapability to observe elements separately. Fig.2B

2200
2000
1800
1600
1400
1200
1000
800
600
400
200
0

A

2s
Oxygen3s
510shows SXE spectra of aqueous Iron(III) chloride,B

in core orbitals, oxygen of H2O and iron ofFe(III)Cl3 is observed at different region of the SXEspectra.

softx-rayabsorptionand3035Fe3+Lα,LβFe3d→2pKα
O2p→1sx3

Elasticscattering(722eV)

FeCl3 aq.

1 mol/L

500

In the course, the participants will experience

152025
Atomic number

O (H2O)

Intensity [arb. units]

as elements. Owing to difference of binding energy

Iron

2p0

which contains hydrogen, oxygen, iron and chlorine

1s600
Emission energy [eV]700

Fig. 2 (A) binding energies of core orbitals
for the elements of atomic number lessthan 36. (B) SXE spectra of aqueous Iron(III)chloride.

emissionmeasurements for the samples in solid state andaqueous solution. The participants will also
learn principle of soft x-ray spectroscopy, detailof the soft x-ray beamline and the soft x-ray emission spectrometer.
2. Outline of the soft x-ray undulator beamline BL17SU and the experimental apparatus
Soft x-ray beamline BL17SU [20] is constructed to advance the spectroscopic studies for mainly
solid state physics and materials science using high brilliant soft x-ray undulator. A novel insertion
device called a multi- polarization-mode undulator has been developed for BL17SU[21-24]. This
insertion device can be operated as a helical, elliptical, pseudo-linear or pseudo-vertical undulator.
Thus, the intense soft x-ray beam of circularly/linearly polarized light of the soft x-ray beam can beobtained at this beamline. The beamline has branched lines (branch-a and -b) which can be switchedby the pre-focusing mirrors
Vacuumand used alternatively. Eachbranch has high resolution
andhighlyend-stations.

To photodiodefor absprption
measurement

Theavailable energy is ranged

Thin film
window(150nm thick)between 300 and 1800 eV.
Typicalresolving

Atomosphere

To emission spectrometerstabilized

monochromator [20, 25] andseveral

ICF114flangeSampleintet/outlet

Incident
beam

power

E/ΔE of the monochromator
is higher than 10,000 and thephoton flux is of the order ofFig. 3 Schematic drawing of liquid flow cell for soft x-ray spectroscopy2

1011 photons/s.
End-stations at BL17SU beamline are actively used for studies of surface adsorbates, liquids,solutions and solids using photoemission, photoabsoprtion, SXE spectroscopies and soft x-ray
diffraction. In the course, the participants will use the end station for liquids and solutions, which islocated at the branch-a. The apparatus consists of the SXE spectrometer, which named High
Efficiency Photon Analyzer (HEPA) [26, 27], and the main chamber equipped with the compact
flange-mount liquid flow-cell which is designed for the studies of liquids under ambient condition.
Fig.3 shows liquid flow cell which utilize ultrathin film of SiN or SiC with 150nm thick as a windows to
separate vacuum and sample an atmosphere.

3. Experimental procedure
3.1 Preparation of the powdered sample
In the beginning of the course, the participants will be asked to prepare the powdered sample.
The sample will be supported by the carbon tape sticked on the sample holder.
3.2 Explanation of the beamline and the SXE spectroscopy
During the evacuation of the chamber, the whole of the beamline as well as the principles of theHEPA spectrometer will be explained to the participants.
3.3 Calibration of the beamline monochromator
After the explanation, calibration of the beamline monochromator will be performed by using ahemispherical electron energy analyzer (SES-2002, VG-SCIENTA) installed at the different
station at a-branch. The kinetic energy spectrum of Au 4f electrons will be measured as afunction of the exciting photon energy in order to check the relationship between thewavelength of the exciting photons and the setup of the beamline monochromator.
3.4 Soft x-ray absorption (SXA) and SXE measurements for solid powder samples
When the vacuum of the chamber is ready for the measurement, XA spectra of the powderedsample in near O 1s-edge region will be measured by means of the total photon yield (TPY)
method. After the XA spectrum measurement, calibration of the HEPA spectrometer will be
carried out by measuring the elastically scattered photons from the sample. Resonant SXEmeasurements will be performed at some energy points where the XA spectrum shows
characteristic features.
3.5 Change the setup of the HEPA spectrometer for the measurement of liquid samples
When the SXE measurements for the powdered sample has finished, the participants are asked
to change the setup of the HEPA spectrometer to be a setup for the liquid sample measurement.
During the evacuation of the chamber, a preparation of the liquid sample will be carried out.
3.6 SXA and SXE measurements of liquid samples
Prior to the SXE measurement, the HEPA spectrometer will be adjusted for the measurements ofthe liquid sample. When conditions are ready for the measurement, an XA spectrum of theliquid sample in near O 1s-edge region will be performed by means of the TPY method.
Resonant SXE measurements will be performed at some energy points as in the case of the3

powdered sample.
3.7 Data analysis and discussions
When all the measurements are finished, the spectrum for each sample will be analyzed andcompared. The participants are now able to compare the results of the SXE measurements forsolid and liquid samples.
References
1.
2.

3.

4.

5.

6.

7.

8.

9.

10.

11.
12.

13.

14.
15.

16.

J. Nordgren, G. Bray, S. Cramm, R. Nyholm, J.E. Rubensson,N. Wassdahl, Soft x-ray emission spectroscopy using
monochromatized synchrotron radiation (invited). Review of Scientific Instruments, 1989. 60(7): p. 1690-1696.
J.H. Guo, Y. Luo, A. Augustsson, J.E. Rubensson, C. Såthe, H. Ågren, H. Siegbahn,J. Nordgren, X-ray emission
spectroscopy of hydrogen bonding and electronic structure of liquid water. Physical Review Letters, 2002. 89(13):p. 137402.
O. Fuchs, M. Zharnikov, L. Weinhardt, M. Blum, M. Weigand, Y. Zubavichus, M. Bar, F. Maier, J.D. Denlinger, C.
Heske, M. Grunze,E. Umbach, Isotope and Temperature Effects in Liquid Water Probed by X-Ray Absorption andResonant X-Ray Emission Spectroscopy. Physical Review Letters, 2008. 100(2): p. 027801.
T. Tokushima, Y. Harada, O. Takahashi, Y. Senba, H. Ohashi, L.G.M. Pettersson, A. Nilsson,S. Shin, Highresolution X-ray emission spectroscopy of liquid water: The observation of two structural motifs. Chemical Physics
Letters, 2008. 460(4-6): p. 387-400.
Y. Horikawa, T. Tokushima, Y. Harada, O. Takahashi, A. Chainani, Y. Senba, H. Ohashi, A. Hiraya,S. Shin,
Identification of valence electronic states of aqueous acetic acid in acid–base equilibrium using site-selective X-rayemission spectroscopy. Physical Chemistry Chemical Physics, 2009. 11(39): p. 8676-8679.
Y. Harada, M. Taguchi, Y. Miyajima, T. Tokushima, Y. Horikawa, A. Chainani, Y. Shiro, Y. Senba, H. Ohashi, H.
Fukuyama,S. Shin, Ligand Energy Controls the Heme-Fe Valence in Aqueous Myoglobins. Journal of the PhysicalSociety of Japan, 2009. 78(4): p. 044802.
C. Huang, K.T. Wikfeldt, T. Tokushima, D. Nordlund, Y. Harada, U. Bergmann, M. Niebuhr, T.M. Weiss, Y.
Horikawa, M. Leetmaa, M.P. Ljungberg, O. Takahashi, A. Lenz, L. Ojamae, A.P. Lyubartsev, S. Shin, L.G.M.
Pettersson,A. Nilsson, The inhomogeneous structure of water at ambient conditions. Proceedings of the National
Academy of Sciences of the United States of America, 2009. 106(36): p. 15214-15218.
T. Tokushima, Y. Horikawa, Y. Harada, O. Takahashi, A. Hiraya,S. Shin, Selective observation of the two oxygen
atoms at different sites in the carboxyl group (-COOH) of liquid acetic acid. Physical Chemistry Chemical Physics,
2009. 11(11): p. 1679-1682.
J. Grasjo, E. Andersson, J. Forsberg, L. Duda, E. Henke, W. Pokapanich, O. Bjorneholm, J. Andersson, A. Pietzsch,
F. Hennies,J.E. Rubensson, Local Electronic Structure of Functional Groups in Glycine As Anion, Zwitterion, andCation in Aqueous Solution. Journal of Physical Chemistry B, 2009. 113(49): p. 16002-16006.
J. Grasjo, E. Andersson, J. Forsberg, E.F. Aziz, B. Brena, C. Johansson, J. Nordgren, L. Duda, J. Andersson, F.
Hennies, J.E. Rubensson,P. Hansson, Electronic Structure of Water Molecules Confined in a Micelle Lattice.
Journal of Physical Chemistry B, 2009. 113(24): p. 8201-8205.
Y. Horikawa, T. Tokushima, A. Hiraya,S. Shin, Pronounced polarization anisotropy in resonant X-ray emission
from acetic acid molecules in solution. Physical Chemistry Chemical Physics, 2010. 12(32): p. 9165-9168.
T. Tokushima, Y. Harada, Y. Horikawa, O. Takahashi, Y. Senba, H. Ohashi, L.G.M. Pettersson, A. Nilsson,S. Shin,High resolution X-ray emission spectroscopy of water and its assignment based on two structural motifs. Journal ofElectron Spectroscopy and Related Phenomena, 2010. 177(2-3): p. 192-205.
E.F. Aziz, K.M. Lange, R. Konnecke, S. Ghadimi, R. Golnak, M.A. Soldatov, K.F. Hodeck,A. Soldatov, Highresolution X-ray emission spectroscopy of water and aqueous ions using the micro-jet technique. Chemical Physics,
2010. 377(1-3): p. 1-5.
K.M. Lange, K.F. Hodeck, U. Schade,E.F. Aziz, Nature of the Hydrogen Bond of Water in Solvents of Different
Polarities. Journal of Physical Chemistry B, 2010. 114(50): p. 16997-17001.
K.M. Lange, R. Könnecke, M. Soldatov, R. Golnak, J.-E. Rubensson, A. Soldatov,E.F. Aziz, On the Origin of theHydrogen-Bond-Network Nature of Water: X-Ray Absorption and Emission Spectra of Water–Acetonitrile Mixtures.
Angewandte Chemie, 2011: p. doi: 10.1002/ange.201104161.
T. Tokushima, Y. Horikawa, H. Arai, Y. Harada, O. Takahashi, L.G.M. Pettersson, A. Nilsson,S. Shin, Polarization
dependent resonant x-ray emission spectroscopy of D[sub 2]O and H[sub 2]O water: Assignment of the local

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17.

18.
19.

20.

21.
22.
23.
24.

25.

26.
27.

molecular orbital symmetry. The Journal of Chemical Physics, 2012. 136(4): p. 044517-7.
H. Arai, Y. Horikawa, K. Sadakane, T. Tokushima, Y. Harada, Y. Senba, H. Ohashi, Y. Takata,S. Shin, Hydrogenbonding of water in 3-methylpyridine studied by O 1s X-ray emission and absorption spectroscopy. PhysicalChemistry Chemical Physics, 2012. 14(5): p. 1576-1580.
J. Stöhr, NEXAFS spectroscopy. Springer series in surface sciences ; 25.1992, Berlin ; New York: Springer-Verlag.
A.C. Thompson, D.T. Attwood, E.M. Gullikson, M.R. Howells, J.B. Kortright, A.L. Robinson, J.H. Underwood,K.-J. Kim, J. Kirz, I. Lindau, P. Pianetta, H. Winick, G.P. Williams,J.H. Scofield, X-Ray Data Booklet,
LBNL/PUB-490 Rev. 2. X-Ray Data Booklet, ed. A.C. Thompson and D. Vaughan2001, Berkeley, CA: Lawrence
Berkeley Laboratory, University of California.
H. Ohashi, Y. Senba, H. Kishimoto, T. Miura, E. Ishiguro, T. Takeuchi, M. Oura, K. Shirasawa, T. Tanaka, M.
Takeuchi, K. Takeshita, S. Goto, S. Takahashi, H. Aoyagi, M. Sano, Y. Furukawa, T. Ohata, T. Matsushita, Y.
Ishizawa, S. Taniguchi, Y. Asano, Y. Harada, T. Tokushima, K. Horiba, H. Kitamura, T. Ishikawa,S. Shin,
Performance of a Highly Stabilized and High-resolution Beamline BL17SU for Advanced Soft X-ray Spectroscopy
at SPring-8. AIP Conference Proceedings, 2007. 879(1): p. 523-526.
T. Tanaka, K. Shirasawa,H. Kitamura, Consideration on an undulator magnetic structure for polarization control.
Review of Scientific Instruments, 2002. 73(4): p. 1724-1727.
K. Shirasawa, T. Tanaka, T. Seike, A. Hiraya,H. Kitamura, Development of multi-polarization-mode undulator. AIP
Conference Proceedings, 2004. 705: p. 203-206.
K. Shirasawa, A. Hiraya, T. Tanaka,H. Kitamura, Optimization of asymmetric figure-8 undulator as circularlypolarized light source. Physical Review Special Topics-Accelerators and Beams, 2004. 7(2): p. 020702.
M. Oura, T. Nakamura, T. Takeuchi, Y. Senba, H. Ohashi, K. Shirasawa, T. Tanaka, M. Takeuchi, Y. Furukawa, T.
Hirono, T. Ohata, H. Kitamura,S. Shin, Degree of circular polarization of soft X-rays emitted from amulti-polarization-mode undulator characterized by means of magnetic circular dichroism measurements. Journalof Synchrotron Radiation, 2007. 14: p. 483-486.
Y. Senba, H. Ohashi, H. Kishimoto, T. Miura, S. Goto, S. Shin, T. Shintake,T. Ishikawa, Fundamental Techniquesfor High Photon Energy Stability of a Modern Soft X-ray Beamline. AIP Conference Proceedings, 2007. 879(1): p.
718-721.
T. Tokushima, Y. Harada, H. Ohashi, Y. Senba,S. Shin, High performance slit-less spectrometer for soft x-rayemission spectroscopy. Review of Scientific Instruments, 2006. 77(6): p. 063107.
T. Tokushima, Y. Horikawa,S. Shin, Triple-path collector optics for grazing incident x-ray emission spectrometer.
Review of Scientific Instruments, 2011. 82: p. 073108.

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