röntgenabszorpciometria

Röntgenabsorptionsspektroskopie, often abbreviated as XAS, is a powerful spectroscopic technique used to study the elemental and chemical composition of materials. It probes the electronic structure of atoms by measuring how much X-ray radiation is absorbed at specific energies. When X-rays of sufficient energy strike an atom, they can excite an electron from an inner shell to a higher energy level or eject it from the atom entirely. This absorption process is highly dependent on the element and its chemical environment.

The XAS spectrum typically shows a sharp rise in absorption, known as an absorption edge, at energies characteristic of a particular element. Above the edge, oscillations in the absorption spectrum, called X-ray Absorption Fine Structure (XAFS), provide detailed information about the local atomic structure surrounding the absorbing atom, including bond distances, coordination numbers, and the types of neighboring atoms.

There are two main modes of XAS: X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS). XANES focuses on the region immediately around the absorption edge and is sensitive to the oxidation state and electronic configuration of the absorbing atom. EXAFS, which extends to higher energies beyond the edge, provides more direct information about the local atomic environment. XAS is a versatile technique applicable to a wide range of materials, including solids, liquids, and gases, and finds applications in fields such as materials science, chemistry, physics, and biology.