The iron L edges: Fe 2p X-ray absorption and electron energy loss spectroscopy

Miedema, Piter S.; Groot, Frank M. F. de

doi:10.1016/j.elspec.2013.03.005

Cited by 133 publications

(131 citation statements)

References 289 publications

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“…The splitting in the L 2 and L 3 bands is due to the 3d t 2g and e g orbital states, as indicated in the brackets [61]. The L 2,3 -edge profiles are similar to those for a-Fe 2 O 3 [62,63], confirming an Fe 3? valence as revealed in the Fe K-edge absorption in Fig.…”

Section: Resultsmentioning

confidence: 58%

Magnetization, phonon, and X-ray edge absorption in barium-doped BiFeO3 ceramics

Yue

Chen

et al. 2016

J Mater Sci

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Magnetization hysteresis loops, dc and ac magnetic susceptibilities, and Raman vibrations have been characterized in (Bi 1-x Ba x )FeO 3-d ceramics for x = 0.0, 0.05, 0.10, and 0.15 as functions of temperature. Ferromagnetic hysteresis loops were observed in Ba-doped compounds with increasing magnetization as Ba substitution increases. High-resolution synchrotron Fe K-and L 2,3 -edge X-ray absorptions reveal an Fe 3? valence and a modification of the Fe-O-Fe bond structure by the A-site Ba substitution. The oxygen K-edge X-ray absorption suggests that the hybridization of the O 2p and Fe 3d orbitals was reduced by the Ba 2? substitution. Field-cooled and zero-field-cooled magnetic susceptibilities reveal a spin-glass behavior, which was enhanced with increasing Ba substitution. Raman vibrations of the Bi-and Fe-sensitive E(2) and A 1 (1) modes reveal frequency softening and step-like anomalies in full-width-at-half-maximum in the vicinity of *150-250 K, which were attributed to spin-phonon interaction while magnetic ordering transitions take place.

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Section: Resultsmentioning

confidence: 58%

Magnetization, phonon, and X-ray edge absorption in barium-doped BiFeO3 ceramics

Yue

Chen

et al. 2016

J Mater Sci

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“…This crystal field splitting value differs from the visible light fitted value of 1.95 eV, 13,26 with the discrepancy attributed to the core-hole altered crystal field strength of the final state in the x-ray transition. 14,27 Transmission electron microscopy The differential absorption at the times indicated in panel a (solid lines) are plotted with the predicted differential absorption spectra for those states (dotted lines). The differential absorption immediately following optical excitation (delay of 0 ps, shown at 0.1 ps in panel a due to the 100 fs offset) matches the prediction for a charge-transfer hybridized state (blue), and the differential absorption at 20 ps matches the prediction for a polaron (red).…”

Section: Xuv Transient Absorption Spectroscopy Utilizes a Visible Or mentioning

confidence: 99%

Photoexcited Small Polaron Formation in Goethite (α-FeOOH) Nanorods Probed by Transient Extreme Ultraviolet Spectroscopy

Porter

Cushing

Carneiro

et al. 2018

J. Phys. Chem. Lett.

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Small polaron formation limits the mobility and lifetimes of photoexcited carriers in metal oxides. As the ligand field strength increases, the carrier mobility decreases, but the effect on the photoexcited small polaron formation is still unknown. Extreme ultraviolet transient absorption spectroscopy is employed to measure small polaron formation rates and probabilities in goethite (α-FeOOH) crystalline nanorods at pump photon energies from 2.2 to 3.1 eV. The measured polaron formation time increases with excitation photon energy from 70  10 fs at 2.2 eV to 350  30 fs at 2.6 eV, whereas the polaron formation probability (85  10%) remains constant. By comparison to hematite (α-Fe2O3), an oxide analog, the role of ligand composition and metal center density in small polaron formation time is discussed. This work suggests that incorporating small changes in ligands and crystal structure could enable the control of photoexcited small polaron formation in metal oxides. TOC GRAPHICSKEYWORDS XUV; extreme-ultraviolet; high-harmonic generation; ligand-to-metal charge transfer; light harvesting; photocatalysis.

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“…An overview of the 2p XAS and XMCD spectra of spinel ferrites have been given by Pearce et al (2006). The Fe L-edge XANES has recently been reviewed by Miedema and de Groot (2013).…”

Section: Transition Metals: L-edgesmentioning

confidence: 99%

X-ray Absorption Near-Edge Structure (XANES) Spectroscopy

Henderson

Groot

Moulton

2014

Reviews in Mineralogy and Geochemistry

262

155

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In addition to the XANES region, at higher energies the extended X-ray absorption fine structure (EXAFS) region is found. The spectral shape in the near-edge region is determined by electronic density of states effects and gives mainly information about the electronic properties and the local geometry of the absorbing atom. The EXAFS region is dominated by single scattering events of the outgoing electron on the neighboring atoms, providing mainly information about the local geometric structure around the absorbing site. In this chapter we will focus on XANES. XANES SpectroscopyIn XPS the ground state (Ψ 0 ) is excited to the ground state plus a core hole (c), where the electron (ε) is excited to higher energy, while in XAS the ground state is excited with a coreto-valence excitation (cv). The XPS binding (E B ) is defined as the photon energy (Ω) minus the measured kinetic energy of the electron (E k ) and corrected for the work function (φ):The work function is the minimal energy to emit an electron from the material. In metals the XAS edge energy can be assumed to be equal to the XPS binding energy, because exactly at the XPS binding energy a transition is possible to the lowest empty state. Experimentally the XAS edge energy can be slightly higher than the XPS binding energy, for example if the transition to the lowest empty state is forbidden by selection rules. Single electron excitation approximation and selection rulesIn first approximation XANES can be described as the excitation of a core electron to an empty state. In the Fermi golden rule, the initial state wave function is rewritten as a core wave function and the final state wave function (ε) as a valence electron wave function (ν). This implicitly assumes that all other electrons do not participate in the X-ray induced transition. In this approximation, the Fermi golden rule can be written as:The X-ray absorption selection rules determine that the dipole matrix element is non-zero if the orbital quantum number of the final state differs by one from the initial state (∆L = ± 1, i.e., s → p, p → s or d, etc.) and the spin is conserved (∆S = 0). In the dipole approximation, the shape of the absorption spectrum should look like the partial density of the (∆L = ± 1) empty states projected on the absorbing site, convoluted with a Lorentzian. This Lorentzian broadening is due to the finite lifetime of the core-hole, leading to an uncertainty in its energy according to Heisenberg's principle. The single electron approximation gives an adequate simulation of the XANES spectral shape if the interactions between the electrons in the final state are relatively weak. This is the case for all excitations from 1s core states (K-edges).

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The iron L edges: Fe 2p X-ray absorption and electron energy loss spectroscopy

Cited by 133 publications

References 289 publications

Magnetization, phonon, and X-ray edge absorption in barium-doped BiFeO3 ceramics

Magnetization, phonon, and X-ray edge absorption in barium-doped BiFeO3 ceramics

Photoexcited Small Polaron Formation in Goethite (α-FeOOH) Nanorods Probed by Transient Extreme Ultraviolet Spectroscopy

X-ray Absorption Near-Edge Structure (XANES) Spectroscopy

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