XASXESmetingen

XASXESmetingen refers to the combined use of X-ray Absorption Spectroscopy (XAS) and X-ray Emission Spectroscopy (XES) to study the electronic structure and local environment of elements in a material. XAS measures how the absorption of X-rays varies with energy near a core-level threshold, providing information on oxidation state, coordination chemistry, and bond distances. Its most common components are XANES (near-edge) and EXAFS (extended fine structure), which reveal electronic structure and local geometry, respectively. XES detects photons emitted as a core hole created by X-ray absorption is filled by electrons from higher shells, yielding spectra that reflect the occupied electronic states, ligand field, and spin state. Together, XAS and XES give a complementary view of both unoccupied and occupied electronic structure.

Experimentally, XAS and XES are typically performed at synchrotron facilities, where a tunable, intense X-ray source enables high-resolution measurements. XAS can be collected in transmission, fluorescence yield, or electron-yield modes, depending on sample thickness and concentration. XES requires energy-dispersive or wavelength-dispersive detectors to resolve characteristic emission lines such as Kα, Kβ, or valence-to-core transitions. Sample environments range from solid-state powders to liquids and nanoparticles and may include in situ conditions like temperature, pressure, or electrochemical bias.

Data analysis involves normalization and calibration of XAS to extract edge energies and pre-edge features, followed by EXAFS fitting to derive bond lengths and coordination numbers. XES spectra are compared to reference compounds to infer oxidation and spin states and ligand-field effects. Software tools commonly used include packages for XAS/EXAFS fitting and for XES interpretation. Applications span catalysis, materials science, chemistry, and biology, where detailed electronic and structural information at the atomic level is required.