The Al K alpha, 1486.6 eV, based x-ray photoelectron spectroscopy (XPS) of Fe 2p and Fe 3p for Fe(III) in Fe2O3 and Fe(II) in FeO is compared with theoretical predictions based on ab initio wavefunctions that accurately treat the final, core-hole, multiplets. The principal objectives of this comparison are to understand the multiplet structure and to evaluate the use of both the 2p and 3p spectra in determining oxidation states. In order to properly interpret the features of these spectra and to use the XPS to provide atomistic insights as well as atomic composition, it is necessary to understand the origin of the multiplet energies and intensities. The theoretical treatment takes into account the ligand field and spin–orbit splittings, the covalent mixing of ligand and Fe 3d orbitals, and the angular momentum coupling of the open shell electrons. These effects lead to the distribution of XPS intensity into a large number of final, ionic, states that are only partly resolved with energies spread over a wide range of binding energies. For this reason, it is necessary to record the Fe 2p and 3p XPS spectra over a wide energy range, which includes all the multiplets in the theoretical treatment as well as additional shake satellites. We also evaluate the effects of differing assumptions concerning the extrinsic background subtraction, to make sure our experimental spectrum may be fairly compared to the theory. We conclude that the Fe 3p XPS provides an additional means for distinguishing Fe(III) and Fe(II) oxidation states beyond just using the Fe 2p spectrum. In particular, with the use of the Fe 3p XPS, the depth of the material probed is about 1.5 times greater than for the Fe 2p XPS. In addition, a new type of atomic many-body effect that involves excitations into orbitals that have Fe f,ℓ = 3, symmetry has been shown to be important for the Fe 3p XPS.
REFERENCES
1.
R. P.
Gupta
and S. K.
Sen
, “Calculation of multiplet structure of core p-vacancy levels. II
,” Phys. Rev. B
12
, 15
(1975
).2.
R. P.
Gupta
and S. K.
Sen
, “Calculation of multiplet structure of core p-vacancy levels
,” Phys. Rev. B
10
, 71
(1974
).3.
A. J.
Freeman
, P. S.
Bagus
, and J. V.
Mallow
, “Multiplet hole theory of core electron binding energies in transition metal ions
,” Int. J. Mag.
4
, 35
(1973
).4.
T.
Yamashita
and P.
Hayes
, “Analysis of XPS spectra of Fe2+ and Fe3+ ions in oxide materials
,” Appl. Surf. Sci.
254
, 2441
(2008
).5.
T.
Yamashita
and P.
Hayes
, “Effect of curve fitting parameters on quantitative analysis of Fe0.94O and Fe2O3 using XPS
,” J. Electron Spectrosc. Relat. Phenom.
152
, 6
(2006
).6.
P. S.
Bagus
et al., “Analysis of the Fe 2p XPS for hematite α Fe2O3: Consequences of covalent bonding and orbital splittings on multiplet splittings
,” J. Chem. Phys.
152
, 014704
(2020
).7.
P. S.
Bagus
et al., “Covalency in Fe2O3 and FeO: Consequences for XPS satellite intensity
,” J. Chem. Phys.
153
, 194702
(2020
).8.
J. L.
Campbell
and T.
Papp
, “Widths of the atomic K–N7 levels
,” At. Data Nucl. Data Tables
77
, 1
(2001
).9.
C. S.
Fadley
, “Basic concepts of X-ray photoelectron spectroscopy
,” in Electron Spectroscopy: Theory, Techniques and Applications
, edited by C. R.
Brundle
and A. D.
Baker
(Academic Press
, 1978
), Vol. 2, p. 2
.10.
P. S.
Bagus
, E. S.
Ilton
, and C. J.
Nelin
, “The interpretation of XPS spectra: Insights into materials properties
,” Surf. Sci. Rep.
68
, 273
(2013
).11.
P. S.
Bagus
, E. S.
Ilton
, and C. J.
Nelin
, “Extracting chemical information from XPS spectra: A perspective
,” Catal. Lett.
148
, 1785
(2018
).12.
J. S.
Griffith
, The Theory of Transition-Metal Ions
(Cambridge University Press
, Cambridge
, 1971
).13.
P. S.
Bagus
et al., “Atomic many-body effects for the p-shell photoelectron spectra of transition metals
,” Phys. Rev. Lett.
84
, 2259
(2000
).14.
15.
J. C.
Slater
, Quantum Theory of Atomic Structure
(McGraw-Hill
, New York
, 1960
), Vols. I and II.16.
A.
Abragam
and B.
Bleaney
, Electron Paramagnetic Resonance of Transition Ions
(Clarendon Press
, Oxford
, 1970
).17.
A. P.
Grosvenor
et al., “Investigation of multiplet splitting of Fe 2p XPS spectra and bonding in iron compounds
,” Surf. Interface Anal.
36
, 1564
(2004
).18.
P. S.
Bagus
, A. J.
Freeman
, and F.
Sasaki
, “Prediction of new multiplet structure in photoemission experiments
,” Phys. Rev. Lett.
30
, 850
(1973
).19.
P. S.
Bagus
, R.
Broer
, and E. S.
Ilton
, “A new near degeneracy effect for photoemission in transition metals
,” Chem. Phys. Lett.
394
, 150
(2004
).20.
P. S.
Bagus
, R.
Broer
, and E. S.
Ilton
, “Atomic near-degeneracy for photoemission: Generality of 4f excitations
,” J. Electron Spectrosc. Relat. Phenom.
165
, 46
(2008
).21.
T.
Åberg
, “Theory of X-ray satellites
,” Phys. Rev.
156
, 35
(1967
).22.
R.
Manne
and T.
Åberg
, Chem. Phys. Lett.
7
, 282
(1970
).23.
K.
Okada
, A.
Kotani
, and B. T.
Thole
, “Charge transfer satellites and multiplet splitting in X-ray photoemission spectra of late transition metal halides
,” J. Electron Spectrosc. Relat. Phenom.
58
, 325
(1992
).24.
K.
Okada
and A.
Kotani
, “Interatomic and intra-atomic configuration interaction in core-level X-ray photoemission spectra of late transition-metal compounds
,” J. Phys. Soc. Jpn.
61
, 4619
(1992
).25.
C. J.
Powell
and J. M.
Conny
, “Evaluation of uncertainties in X-ray photoelectron spectroscopy intensities associated with different methods and procedures for background subtraction. I. Spectra for monochromatic Al X-ray
,” Surf. Interface Anal.
41
, 269
(2009
).26.
See https://www.kratos.com/application-areas/application-downloads/lateral-resolution-AXIS-instruments for Resolution of the Kratos AXIS Ultra, Kratos, 2020.
27.
See https://xpssimplified.com/kalpha_surface_analysis.php for Thermo Scientific XPS—K-Alpha.
28.
See https://kristalle.com/product/hematite-3/ for South African Hematite—Natural mineral.
29.
See https://api.sigmaaldrich.com/deepweb/assets/sigmaaldrich/quality/spec/367/575/400866-BULK_______ALDRICH__.pdf for Aldrich FeO powder.
30.
M.
Zong
et al., “Synthesis of 2D hexagonal hematite nanosheets and the crystal growth mechanism
,” Inorg. Chem.
58
, 16727
(2019
).31.
K. S.
Kim
et al., “ESCA studies of metal-oxygen surfaces using argon and oxygen ion-bombardment
,” J. Electron Spectrosc. Relat. Phenom.
5
, 351
(1974
).32.
N. S.
McIntyre
and D. G.
Zetaruk
, “X-ray photoelectron spectroscopic studies of iron oxides
,” Anal. Chem.
49
, 1521
(1977
).33.
T. J.
Chuang
, C. R.
Brundle
, and K.
Wandelt
, “An X-ray photoelectron spectroscopy study of the chemical changes in oxide and hydroxide surfaces induced by Ar+ ion bombardment
,” Thin Solid Films
53
, 19
(1978
).34.
D. A.
Shirley
, “High-resolution X-ray photoemission spectrum of the valence bands of gold
,” Phys. Rev. B
5
, 4709
(1972
).35.
A.
Proctor
and P. M. A.
Sherwood
, “Data analysis techniques in x-ray photoelectron spectroscopy
,” Anal. Chem.
54
, 13
(1982
).36.
T.
Droubay
and S. A.
Chambers
, “Surface-sensitive Fe 2p photoemission spectra for α-Fe2O3(0001): The influence of symmetry and crystal-field strength
,” Phys. Rev. B
64
, 205414
(2001
).37.
M. B.
Sanchez
et al., “Composition assessment of ferric oxide by accurate peak fitting of the Fe 2p photoemission spectrum
,” Surf. Interface Anal.
49
, 253
(2017
).38.
N.
Pauly
et al., “XPS primary excitation spectra of Zn 2p, Fe 2p, and Ce 3d from ZnO, α-Fe2O3, and CeO2
,” Surf. Interface Anal.
51
, 353
(2019
).39.
M.
Aronniemi
, J.
Sainio
, and J.
Lahtinen
, “Chemical state quantification of iron and chromium oxides using XPS: The effect of the background subtraction method
,” Surf. Sci.
578
, 108
(2005
).40.
S.
Tougaard
, “Formalism for quantitative surface analysis by electron spectroscopy
,” J. Vac. Sci. Technol., A
8
, 2197
(1990
).41.
C. S.
Lawson
, B. J.
Tielsch
, and J. E.
Fulghum
, “Study of the first row transition metals by X-ray photoelectron spectroscopy
,” Surf. Sci. Spectra
4
, 316
(1996
).42.
43.
H. M.
Evjen
, “On the stability of certain heteropolar crystals
,” Phys. Rev.
39
, 675
(1932
).44.
P. S.
Bagus
, M. J.
Sassi
, and K. M.
Rosso
, “Cluster embedding of ionic systems: Point charges and extended ions
,” J. Chem. Phys.
151
, 044107
(2019
).45.
P. S.
Bagus
et al., “Consequences of realistic embedding for the L2,3 edge XAS of α-Fe2O3
,” Phys. Chem. Chem. Phys.
20
, 4396
(2018
).46.
C.
de Graaf
, C.
Sousa
, and R.
Broer
, “Ionization and excitation energies in CuCl and NiO within different embedding schemes
,” J. Mol. Struct.: THEOCHEM
458
, 53
(1998
).47.
48.
T.
Saue
, “Relativistic Hamiltonians for chemistry: A primer
,” ChemPhysChem
12
, 3077
(2011
).49.
L.
Visscher
et al., “Relativistic quantum chemistry: The MOLFDIR program package
,” Comput. Phys. Commun.
81
, 120
(1994
).50.
P.-O.
Löwdin
, “Quantum theory of many-particle systems. I. Physical interpretations by means of density matrices, natural spin-orbitals, and convergence problems in the method of configurational interaction
,” Phys. Rev.
97
, 1474
(1955
).51.
P. S.
Bagus
et al., “Origin of the 3p XPS of 3d transition metal atoms and compounds
” (unpublished).52.
S. L.
Altmann
and P.
Herzig
, Point-Group Theory Tables
(Clarendon Press
, Oxford
, 1994
).53.
C.
Sousa
, P. S.
Bagus
, and F.
Illas
, “Approaching multiplet splitting in X-ray photoelectron spectra by density functional theory methods: NO and O2 molecules as examples
,” Chem. Phys. Lett.
731
, 136617
(2019
).54.
P. S.
Bagus
and E. S.
Ilton
, “Atomic many-body effects in the 4f XPS of the U5+ and U4+ cations: Part II: Consequences of orbital relaxation
,” Theor. Chem. Acc.
118
, 495
(2007
).55.
P. S.
Bagus
, E. S.
Ilton
, and J. R.
Rustad
, “Ligand-field effects for the 3p photoelectron spectra of Cr2O3
,” Phys. Rev. B
69
, 205112
(2004
).56.
P. S.
Bagus
et al., “Multiplet splitting for the XPS of heavy elements: Dependence on oxidation state
,” Surf. Sci.
643
, 142
(2016
).57.
P. S.
Bagus
and C. J.
Nelin
, “Covalent interactions in oxides
,” J. Electron Spectrosc. Relat. Phenom.
194
, 37
(2014
).58.
P. S.
Bagus
, M. J.
Sassi
, and K. M.
Rosso
, “Intermediate coupling for core-level excited states: Consequences for X-ray absorption spectroscopy
,” J. Electron Spectrosc. Relat. Phenom.
200
, 174
(2015
).59.
60.
P. S.
Bagus
et al., “Anomalous multiplet-splitting intensity ratios in K-level x-ray photoemission
,” Phys. Rev. A
9
, 1090
(1974
).61.
F.
Prosser
and S.
Hagstrom
, “On the rapid computation of matrix elements
,” Int. J. Quantum Chem.
2
, 89
(1968
).62.
B. D.
Hermsmeier
et al., “Energy dependence of the outer core-level multiplet structures in atomic Mn and Mn-containing compounds
,” Phys. Rev. B
48
, 12425
(1993
).63.
J. A.
Gubner
, “A new series for approximating Voigt functions
,” J. Phys. A: Math. Gen.
27
, L745
(1994
).64.
G. K.
Wertheim
et al., “Determination of the Gaussian and Lorentzian content of experimental line shapes
,” Rev. Sci. Instrum.
45
, 1369
(1974
).65.
P. H.
Citrin
, P.
Eisenberger
, and D. R.
Hamann
, “Phonon broadening of X-ray photoemission linewidths
,” Phys. Rev. Lett.
33
, 965
(1974
).66.
M.
Iwan
and C.
Kunz
, “Investigation of the phonon broadening of core levels in NaCl
,” Phys. Lett. A
60
, 345
(1977
).67.
C. J.
Nelin
et al., “Analysis of the broadening of X-ray photoelectron spectroscopy peaks for ionic crystals
,” Angew. Chem., Int. Ed.
50
, 10174
(2011
).68.
R.
Unwin
et al., “The effect of a resonance of vibrational structure in the photoelectron spectrum of acetylene
,” Chem. Phys. Lett.
77
, 242
(1981
).69.
M.
Taguchi
, T.
Uozumi
, and A.
Kotani
, “Theory of X-ray photoemission and X-ray emission spectra in Mn compounds
,” J. Phys. Soc. Jpn.
66
, 247
(1997
).70.
K.
Tiedtke
et al., “Term-dependent lifetime broadening in the 3p photoelectron spectra of atomic Fe and Co
,” Phys. Rev. A
64
, 022705
(2001
).71.
DIRAC, a relativistic ab initio electronic structure program, Release DIRAC08, written by
L.
Visscher
, H. J. A.
Jensen
, and T.
Saue
, with new contributions from R.
Bast
, S.
Dubillard
, K. G.
Dyall
, U.
Ekström
, E.
Eliav
, T.
Fleig
, A. S. P.
Gomes
, T. U.
Helgaker
, J.
Henriksson
, M.
Iliaš
, Ch. R.
Jacob
, S.
Knecht
, P.
Norman
, J.
Olsen
, M.
Pernpointner
, K.
Ruud
, P.
Sałek
, and J.
Sikkema
; see the URL at http://dirac.chem.sdu.dk, 2008
.72.
CLIPS is a program system to compute ab initio SCF and correlated wavefunctions for polyatomic systems. It has been developed based on the publicly available programs in the ALCHEMY package from the IBM San Jose Research Laboratory by
P. S.
Bagus
, B.
Liu
, A. D.
McLean
, and M.
Yoshimine
.73.
P. S.
Bagus
et al., “Analysis of X-ray adsorption edges: L2,3 edge of FeCl4−
,” J. Chem. Phys.
147
, 224306
(2017
).74.
P. S.
Bagus
and E. S.
Ilton
, “Effects of covalency on the p-shell photoemission of transition metals: MnO
,” Phys. Rev. B
73
, 155110
(2006
).75.
W. L.
Jolly
, “The estimation of core-electron binding-energy shifts using the concept of the equivalence of equally charged cores
,” in Proceedings of the International Conference on Electron Spectroscopy
, edited by D. A.
Shirley
(North-Holland
, Amsterdam, The Netherlands
, 1972
), p. 629
.76.
J. C.
Fuggle
and S. F.
Alvarado
, “Core-level lifetimes as determined by x-ray photoelectron spectroscopy measurements
,” Phys. Rev. A
22
, 1615
(1980
).77.
R.
Nyholm
et al., “Auger and Coster–Kronig broadening effects in the 2p and 3p photoelectron spectra from the metals 22Ti-30Zn
,” J. Phys. F: Met. Phys.
11
, 1727
(1981
).© 2021 Author(s).
2021
Author(s)
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