Röntgenabsorptionsspektroskopi

Röntgenabsorptionsspektroskopie, often abbreviated as XAS, is a spectroscopic technique used to investigate the electronic and structural properties of materials. It relies on the absorption of X-rays by atoms within a sample. When X-rays with sufficient energy impinge upon an atom, they can excite an inner-shell electron, causing the atom to absorb the X-ray photon. The energy required for this excitation is characteristic of the specific element and its chemical environment.

The absorption spectrum obtained from XAS reveals distinct features. Near the absorption edge of an element, known as the X-ray absorption near-edge structure (XANES), the absorption spectrum is sensitive to the oxidation state and coordination geometry of the absorbing atom. Further away from the absorption edge, in the extended X-ray absorption fine structure (EXAFS) region, oscillations in the absorption spectrum provide information about the distances and types of neighboring atoms.

XAS is a versatile technique that can be applied to a wide range of materials, including solids, liquids, and gases. It is element-specific, meaning that the absorption spectrum provides information about individual elements within a complex sample. Applications of XAS span various scientific disciplines, including materials science, chemistry, physics, and biology, where it is used to characterize catalysts, study electronic devices, analyze geological samples, and probe biological molecules.