On the Multipole Character of the X‐Ray Transitions in the Pre‐Edge Structure of Fe K Absorption Spectra. An Experimental Study

Dräger, G.; Frahm, R.; Materlik, G.; Brümmer, O.

doi:10.1002/pssb.2221460130

Cited by 138 publications

(88 citation statements)

References 18 publications

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“…The high dispersion of the Fe phase is underlined by the complete absence of pre-edge spectral contributions centered above 7115.0 eV. Their presence, reported in the literature to increase with the degree of Fe(O,OH) 6 -octahedral polymerization (ferrihydrite < goethite < hematite) [34,35], is, on the contrary, clearly visible in the pre-edge peak of the measured hematite (Figs. 8 and 9).…”

Section: Washingmentioning

confidence: 69%

“…Prior to calculations, the pre-edge of α-Fe 2 O 3 was deconvoluted into pseudo-Voigt components (50% Gaussian, 50% Lorentzian peaks shape). Contribution to the centroid position and to the integrated intensity from components centered above 7115.0 eV was ignored [34,35]. The estimated accuracy in the energy determination for the HR-XANES spectra presented in this study is ±0.05 eV.…”

Section: Hr-xanes Data Collection and Processingmentioning

confidence: 89%

“…Some small tailing appeared in the Fe K-pre-edges after calcination at energies above 7115.0 eV. This contribution, which is more pronounced in the severely calcined sample, is ascribed to the presence of three-dimensional polymerization of part of iron [34,35].…”

Section: Calcinationmentioning

confidence: 92%

“…Peaks 1 and 2, centered respectively at 7112.65 and 7114.05 eV, are related to 1s → 3d (quadrupolar) and/or 1s → 4p (dipolar) metal electronic transitions [35,54,55]. Contributions 3 and 4 centered above 7115.0 eV (7115.34 and 7116.88 eV) are due to extra transitions involving 3d orbitals of distant iron neighbors [35]. Contributions 3 and 4 were not included in the determination of the reference preedge area and centroid position.…”

Section: Al Mas Nmr Al K-edge Xafsmentioning

confidence: 99%

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Evolution of Fe species during the synthesis of over-exchanged Fe/ZSM5 obtained by chemical vapor deposition of FeCl3

Battiston

Bitter

Groot

et al. 2003

Journal of Catalysis

163

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The evolution of iron in over-exchanged Fe/ZSM5 prepared via chemical vapor deposition of FeCl 3 was studied at each stage of the synthesis. Different characterization techniques (EXAFS, HR-XANES, 57 Fe Mössbauer spectroscopy, 27 Al NMR, EELS, HR-TEM, XRD, N 2 physisorption, and FTIR spectroscopy) were applied in order to correlate the changes occurring in the local environment of the Fe atoms with migration and aggregation phenomena of iron at micro-and macroscopic scale. Mononuclear isolated Fe-species are formed upon FeCl 3 sublimation, which are transformed into binuclear Fe-complexes during washing. During calcination, iron detached from the Brønsted sites migrates to the external surface of the zeolite, finally leading to significant agglomeration. Nevertheless, agglomeration of Fe can be strongly suppressed by adequately tuning the conditions of the calcination.  2002 Elsevier Science (USA). All rights reserved.

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Section: Washingmentioning

confidence: 69%

Section: Hr-xanes Data Collection and Processingmentioning

confidence: 89%

Section: Calcinationmentioning

confidence: 92%

Section: Al Mas Nmr Al K-edge Xafsmentioning

confidence: 99%

See 2 more Smart Citations

Evolution of Fe species during the synthesis of over-exchanged Fe/ZSM5 obtained by chemical vapor deposition of FeCl3

Battiston

Bitter

Groot

et al. 2003

Journal of Catalysis

163

View full text Add to dashboard Cite

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“…Thus, in calculations using a finite basis set, the magnetic-dipole and magneticquadrupole transition moments do not show the exact origin dependence of Eqs. (54) and (56).…”

Section: Isotropic Averagingmentioning

confidence: 99%

Origin-independent calculation of quadrupole intensities in X-ray spectroscopy

Bernadotte

Atkins

Jacob

2012

The Journal of Chemical Physics

147

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For electronic excitations in the ultraviolet and visible range of the electromagnetic spectrum, the intensities are usually calculated within the dipole approximation, which assumes that the oscillating electric field is constant over the length scale of the transition. For the short wavelengths used in hard X-ray spectroscopy, the dipole approximation may not be adequate. In particular, for metal K-edge X-ray absorption spectroscopy (XAS), it becomes necessary to include higher-order contributions. In quantum-chemical approaches to X-ray spectroscopy, these socalled quadrupole intensities have so far been calculated by including contributions depending on the square of the electric-quadrupole and magnetic-dipole transition moments. However, the resulting quadrupole intensities depend on the choice of the origin of the coordinate system. Here, we show that for obtaining an originindependent theory, one has to include all contributions that are of the same order in the wave vector consistently. This leads to two additional contributions depending on products of the electric-dipole andelectric-octupole and of the electric-dipole and magnetic-quadrupole transition moments, respectively. We have implemented such an origin-independent calculation of quadrupole intensities in XAS within timedependent density-functional theory, and demonstrate its usefulness for the calculation of metal and ligand K-edge XAS spectra of transition metal complexes.2

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Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

Vedrinskiǐ

Крайзман

Novakovich

et al. 2001

phys. stat. sol. (b)

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Polarized Ni K XANES of single crystal NiO is studied experimentally and theoretically for two crystal orientations relative to the polarization and wave vectors of incident X-ray beam. The spectra calculated by the full multiple scattering method for a spin-dependent cluster potential and incomplete screening of the core hole appear to be in an excellent agreement with the experiment. The low energy pre-edge peak is shown to be caused by the quadrupole transitions of the Ni 1s electron to an exciton-type state shifted down by $4 eV from the empty e g high-energy conduction band under the influence of the core hole potential. The feature caused by the Ni 1s ! e g band dipole transitions is also recognized in the spectrum. It is shown that the same mechanisms, which are responsible for the formation of the pre-edge fine structure in the oxides of early 3d-metals in 3d 0 state, work in the considered case as well. A comparative analysis outlining the significance of different mechanisms for the pre-edge structure formation in cases of early and late 3d-metal spectra is presented. The antiferromagnetic order of the absorber is taken into account within oneelectron approximation.Die polarisierte Ni K XANES von einkristallinem NiO wurde experimentell und theoretisch fü r zwei Kristallorientierungen relativ zum Polarisations-und Wellenvektor des einfallenden Rö ntgenstrahls untersucht. Die Spektren wurden nach der Full-multiple-scattering Methode fü r ein spinabhä ngiges Clusterpotential und fü r unvollstä ndige Abschirmung des Rumpfloches in exzellenter Ûbereinstimmung mit dem Experiment berechnet. Die niederenergetische Vorkantenabsorption wird durch Quadrupolü bergä nge von Ni 1s Elektronen in einen exzitonä hnlichen Zustand erklä rt, der durch das Rumpflochpotential um $4 eV gegenü ber dem unbesetzten e gartigen Leitungsband abgesenkt ist. Die aus den Ni 1s ! e g Dipolü bergä ngen berechneten Strukturen sind auch in den experimentellen Spektren zu erkennen. Es wird gezeigt, da im vorliegenden Fall die gleichen Mechanismen wirken, die auch fü r das Auftreten der Vorkantenabsorption bei den frü hen 3d-Metalloxiden im 3d 0 -Zustand verantwortlich sind. Eine vergleichende Analyse der Bedeutung der verschiedenen Mechanismen fü r das Entstehen der Vorkantenstruktur bei den Verbindungen der 3d-Metalle niedriger und hö herer Ordnungszahl wird durchgefü hrt.

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On the Multipole Character of the X‐Ray Transitions in the Pre‐Edge Structure of Fe K Absorption Spectra. An Experimental Study

Cited by 138 publications

References 18 publications

Evolution of Fe species during the synthesis of over-exchanged Fe/ZSM5 obtained by chemical vapor deposition of FeCl3

Evolution of Fe species during the synthesis of over-exchanged Fe/ZSM5 obtained by chemical vapor deposition of FeCl3

Origin-independent calculation of quadrupole intensities in X-ray spectroscopy

Experimental and Theoretical Studies of Fine Structure in Polarized Ni K X-Ray Absorption Spectra of NiO Single Crystals

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