Effect of Lattice Relaxation on the Soft X-Ray Spectra of Metals

1971 ◽  
Vol 49 (24) ◽  
pp. 3155-3165 ◽  
Author(s):  
B. Bergersen ◽  
T. McMullen ◽  
J. P. Carbotte
Keyword(s):  
Harmonic Approximation ◽  
Lattice Relaxation ◽  
Linear Response Theory ◽  
Scattering Data ◽  
Core Hole ◽  
X Ray ◽  
The Core ◽  
Relaxation Effects ◽  
Order Of Magnitude ◽  
Lifetime Effects

The effect of relaxation of the lattice around the core hole on the soft X-ray spectra of metals near the Fermi edge, with particular application to Li and Na, is investigated. Neglecting lifetime effects, linearizing the core-hole phonon coupling and making a harmonic approximation for the phonons, the problem is exactly solvable by a generalization of a method previously proposed by Langreth to finite temperatures. Numerical calculations are carried out within the framework of linear response theory using the Thomas–Fermi, R.P.A., and Singwi et al. dielectric functions, and realistic phonon spectra obtained from neutron inelastic scattering data. The calculations give rise to lattice relaxation effects of similar magnitude in both metals. The results are considerably smaller than would be necessary to explain the shape of the Li spectra (contrary to a previous suggestion), while in Na the contribution is calculated to be of the same order of magnitude, but with a different temperature dependence, than the other factors influencing the shape of the absorption edge.

Lifetime Effects in Metal Soft X-Ray Spectra

1972 ◽  
Vol 50 (10) ◽  
pp. 1002-1013 ◽  
Author(s):  
T. McMullen ◽  
B. Bergersen
Keyword(s):  
Solvable Model ◽  
Quantum Statistical Mechanics ◽  
Emission Spectra ◽  
Memory Effects ◽  
Recoil Energy ◽  
Core Hole ◽  
X Ray ◽  
The Core ◽  
Diagrammatic Method ◽  
Lifetime Effects

Methods of nonequilibrium quantum statistical mechanics are applied to the problem of estimating effects arising from the finite lifetime of the core hole in soft X-ray emission spectra. A comparison is made with the formalism for absorption spectra where equilibrium methods are appropriate. A diagrammatic method for estimating lifetime effects is described. It is shown how the validity of the Weisskopf and Wigner approximation is related to two basic assumptions on the decay of the core hole, namely the absence of memory effects and exponential decay of the core hole. Possible memory effects are discussed in detail using a solvable model, and their effect on the spectrum when present is indicated. In particular it is shown that in the model the recoil energy associated with an initial electron bombardment exciting the core, even if appreciable in magnitude, cannot be expected to give rise to a width of the core level, thus broadening the spectrum.

CORE-HOLE EFFECT IN THE Ce L3 X-RAY ABSORPTION SPECTRA OF CeO2 AND CeFe2: NEW EXAMINATION BY USING RESONANT X-RAY EMISSION SPECTROSCOPY

2013 ◽  
Vol 27 (16) ◽  
pp. 1330012 ◽  
Author(s):  
A. KOTANI
Keyword(s):  
Absorption Spectra ◽  
Ground State ◽  
Theoretical Calculations ◽  
Emission Spectra ◽  
Core Hole ◽  
Final State ◽  
X Ray ◽  
The Core ◽  
X Ray Absorption ◽  
Hole Effect

We consider two different resonant X-ray emission spectra for Ce compounds: Ce 3d to 2p X-ray emission (denoted by 3d-RXES) and valence to 2p X-ray emission (v-RXES), both of which follow the Ce 2p to 5d resonant excitation. We propose that the comparison of the 3d- and v-RXES spectra is a new powerful method of directly detecting the core-hole effect in the final state of Ce L 3 X-ray absorption spectra (XAS). We applied this method to recent experimental RXES spectra for CeO 2 and CeFe 2, and showed unambiguously that the core-hole effect should be essential in the XAS of both materials. This result is confirmed by theoretical calculations, which reproduce well the experimental RXES and XAS spectra. We conclude that the ground state of CeO 2 is in the mixed state of 4f0 and [Formula: see text] configurations, where [Formula: see text] is a ligand hole, instead of a pure 4f0 configuration which was proposed recently by first-principles energy band calculations. Also, we conclude that the double peaks observed in L 3 XAS of CeFe 2 are caused by the 4f0 and 4f1 configurations, which are mixed in the ground state but separated in energy by the large core-hole potential in the final state of XAS.

scholarly journals Analysis of a measurement scheme for ultrafast hole dynamics by few femtosecond resolution X-ray pump–probe Auger spectroscopy

2014 ◽  
Vol 171 ◽  
pp. 93-111 ◽  
Author(s):  
Bridgette Cooper ◽  
Přemysl Kolorenč ◽  
Leszek J. Frasinski ◽  
Vitali Averbukh ◽  
Jon P. Marangos
Keyword(s):  
Auger Spectroscopy ◽  
X Rays ◽  
Core Hole ◽  
Pump Probe ◽  
X Ray ◽  
Molecular Systems ◽  
The Core ◽  
Probe Delay ◽  
Valence Region ◽  
Hole Migration

Ultrafast hole dynamics created in molecular systems as a result of sudden ionisation is the focus of much attention in the field of attosecond science. Using the molecule glycine we show through ab initio simulations that the dynamics of a hole, arising from ionisation in the inner valence region, evolves with a timescale appropriate to be measured using X-ray pulses from the current generation of SASE free electron lasers. The examined pump–probe scheme uses X-rays with photon energy below the K edge of carbon (275–280 eV) that will ionise from the inner valence region. A second probe X-ray at the same energy can excite an electron from the core to fill the vacancy in the inner-valence region. The dynamics of the inner valence hole can be tracked by measuring the Auger electrons produced by the subsequent refilling of the core hole as a function of pump–probe delay. We consider the feasibility of the experiment and include numerical simulation to support this analysis. We discuss the potential for all X-ray pump-X-ray probe Auger spectroscopy measurements for tracking hole migration.

scholarly journals Spectral weight of resonant inelastic X-ray scattering in doped cuprates: Effect of core-hole lifetime

2018 ◽  
Vol 32 (17) ◽  
pp. 1840017 ◽  
Author(s):  
Takami Tohyama ◽  
Kenji Tsutsui
Keyword(s):  
Spectral Weight ◽  
Main Peak ◽  
Core Hole ◽  
X Ray ◽  
The Core ◽  
X Ray Scattering ◽  
Spin Flip ◽  
X Ray Absorption ◽  
Magnon Excitation ◽  
Ray Scattering

We examine the effect of core-hole lifetime on the spectral weight of resonant inelastic X-ray scattering (RIXS) in hole-doped cuprates. We calculate the spectral weight by using the exact diagonalization technique for a 4 × 4 doped Hubbard lattice and find that the spin-flip channel detecting single-magnon excitation is less sensitive to the core-hole lifetime while in the non-spin-flip channel the spectral weight is strongly dependent on the lifetime. In the latter, charge and two-magnon excitations predominately contribute to RIXS for short and long core-hole lifetimes, respectively. For a realistic value of the core-hole lifetime in cuprates, both the charge and two-magnon excitations are expected to contribute to the non-spin-flip channel in RIXS when the incident-photon energy is tuned to the main peak of X-ray absorption spectrum.

scholarly journals Finite lifetime broadening of calculated X-ray absorption spectra: possible artefacts close to the edge

2018 ◽  
Vol 25 (2) ◽  
pp. 523-528 ◽  
Author(s):  
Ondřej Šipr ◽  
Jiří Vackář ◽  
Ján Minár
Keyword(s):  
Absorption Spectra ◽  
Real Axis ◽  
Absorption Edge ◽  
Spectral Features ◽  
Core Hole ◽  
Energy Component ◽  
X Ray ◽  
The Core ◽  
X Ray Absorption ◽  
Small Imaginary Part

X-ray absorption spectra calculated within an effective one-electron approach have to be broadened to account for the finite lifetime of the core hole. For methods based on Green's function this can be achieved either by adding a small imaginary part to the energy or by convoluting the spectra on the real axis with a Lorentzian. By analyzing the FeK- andL2,3-edge spectra it is demonstrated that these procedures lead to identical results only for energies higher than a few core-level widths above the absorption edge. For energies close to the edge, spurious spectral features may appear if too much weight is put on broadeningviathe imaginary energy component. Special care should be taken for dichroic spectra at edges which comprise several exchange-split core levels, such as theL3-edge of 3dtransition metals.

scholarly journals TEXS: in-vacuum tender X-ray emission spectrometer with 11 Johansson crystal analyzers

2020 ◽  
Vol 27 (3) ◽  
pp. 813-826 ◽  
Author(s):  
Mauro Rovezzi ◽  
Alistair Harris ◽  
Blanka Detlefs ◽  
Timothy Bohdan ◽  
Artem Svyazhin ◽  
...  
Keyword(s):  
Vacuum Chamber ◽  
Solid Angle ◽  
High Vacuum ◽  
Core Hole ◽  
Innovative Design ◽  
X Ray ◽  
The Core ◽  
First Results ◽  
Sufficient Space

The design and first results of a large-solid-angle X-ray emission spectrometer that is optimized for energies between 1.5 keV and 5.5 keV are presented. The spectrometer is based on an array of 11 cylindrically bent Johansson crystal analyzers arranged in a non-dispersive Rowland circle geometry. The smallest achievable energy bandwidth is smaller than the core hole lifetime broadening of the absorption edges in this energy range. Energy scanning is achieved using an innovative design, maintaining the Rowland circle conditions for all crystals with only four motor motions. The entire spectrometer is encased in a high-vacuum chamber that allocates a liquid helium cryostat and provides sufficient space for in situ cells and operando catalysis reactors.

STUDY OF ELECTRONIC STRUCTURE OF MgB2 BY MULTIPLE-SCATTERING CALCULATIONS OF B K-EDGE XANES

2002 ◽  
Vol 16 (11n12) ◽  
pp. 1605-1612
Author(s):  
ZIYU WU ◽  
N. L. SAINI ◽  
A. BIANCONI
Keyword(s):  
Multiple Scattering ◽  
Density Of States ◽  
Core Hole ◽  
Edge Structure ◽  
X Ray ◽  
The Core ◽  
Al Substitution ◽  
Band Structure Calculations ◽  
X Ray Absorption ◽  
Structure Calculations

The MgB 2 system is studied by self consistent multiple-scattering calculations at the B K-edge X-ray absorption near edge structure (XANES). We find that the features in the B K-edge XANES are strongly affected by medium and long range order with large influence of the core hole potential suggesting that the band structure calculations are not enough to provide a quantitative interpretation of the spectral features. We have investigated evolution of density of states in the conduction band as a function of Al substitution in place of the Mg. The results are consistent with the fact that the Al substitution influences mainly the density of states in the B σ-band and hence suppresses the superconductivity.

Anisotropy of the core-hole relaxation in x-ray-absorption spectroscopy as probed in square planar cuprates

1992 ◽  
Vol 45 (14) ◽  
pp. 8091-8096 ◽  
Author(s):  
H. Tolentino ◽  
M. Medarde ◽  
A. Fontaine ◽  
F. Baudelet ◽  
E. Dartyge ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Core Hole ◽  
X Ray ◽  
The Core ◽  
Square Planar ◽  
X Ray Absorption
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