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Web-Based Methods for X-ray and Photoelectron Spectroscopies

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 Added by Thomas Devereaux
 Publication date 2021
  fields Physics
and research's language is English




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We present a simplified web-based application for simulating x-ray and photoelectron spectra of transition metals, built around the notion that web-based applications lower the bar for novice users. The application provides a simple interface to simulate x-ray absorption spectroscopy, resonant inelastic x-ray scattering, and angle-resolved photoemission spectroscopy, incorporating the effects of local electronic interactions, which give rise to multiplets, spin-orbit coupling, crystal field effects, and ligand hybridization/charge transfer. Results can be obtained that highlight the key role of photon polarization.



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167 - F. Vernay , B. Delley 2009
An easily accessible method is presented that permits to calculate spectra involving atomic multiplets relevant to X-ray Absorption Spectroscopy (XAS) and Resonant Inelastic X-ray Scattering (RIXS) experiments. We present specific examples and compare the calculated spectra with available experimental data
A laboratory hard X-ray photoelectron spectroscopy (HXPS) system equipped with a monochromatic Cr K$alpha$ ($h u = 5414.7$ eV) X-ray source was applied to an investigation of the core-level electronic structure of La$_{1-x}$Sr$_x$MnO$_3$. No appreciable high binding-energy shoulder in the O $1s$ HXPS spectra were observed while an enhanced low binding-energy shoulder structure in the Mn $2p_{3/2}$ HXPS spectra were observed, both of which are manifestation of high bulk sensitivity. Such high bulk sensitivity enabled us to track the Mn $2p_{3/2}$ shoulder structure in the full range of $x$, giving us a new insight into the binding-energy shift of the Mn $2p_{3/2}$ core level. Comparisons with the results using the conventional laboratory XPS ($h u = 1486.6$ eV) as well as those using a synchrotron radiation source ($h u = 7939.9$ eV) demonstrate that HXPS is a powerful and convenient tool to analyze the bulk electronic structure of a host of different compounds.
Soft and hard X-ray photoelectron spectroscopy (PES) has been performed for one of the heavy fermion system CeRu$_2$Si$_2$ and a $4f$-localized ferromagnet CeRu$_2$Ge$_2$ in the paramagnetic phase. The three-dimensional band structures and Fermi surface (FS) shapes of CeRu$_2$Si$_2$ have been determined by soft X-ray $h u$-dependent angle resolved photoelectron spectroscopy (ARPES). The differences in the Fermi surface topology and the non-$4f$ electronic structures between CeRu$_2$Si$_2$ and CeRu$_2$Ge$_2$ are qualitatively explained by the band-structure calculation for both $4f$ itinerant and localized models, respectively. The Ce valences in CeRu$_2X_2$ ($X$ = Si, Ge) at 20 K are quantitatively estimated by the single impurity Anderson model calculation, where the Ce 3d hard X-ray core-level PES and Ce 3d X-ray absorption spectra have shown stronger hybridization and signature for the partial $4f$ contribution to the conduction electrons in CeRu$_2$Si$_2$.
Here we report about the interface reconstruction in the recently discovered superconducting artificial superlattices based on insulating CaCuO2 and SrTiO3 blocks. Hard x-ray photoelectron spectroscopy shows that the valence bands alignment prevents any electronic reconstruction by direct charge transfer between the two blocks. We demonstrate that the electrostatic built-in potential is suppressed by oxygen redistribution in the alkaline earth interface planes. By using highly oxidizing growth conditions, the oxygen coordination in the reconstructed interfaces may be increased, resulting in the hole doping of the cuprate block and thus in the appearance of superconductivity.
Hard X-ray and extremely low energy bulk-sensitive photoelectron spectroscopy has been performed in the temperature range of 100-330 K for Fe3O4. In the high temperature phase just above the Verwey transition, the intensity at the Fermi level (EF) is still negligible, but it increases gradually with further increasing the temperature (250 K, 330 K) in consistence with the temperature dependence of the conductivity. The spectral behaviors near EF with temperature are well explained by the model, which takes the polaron effect into account.
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