uEXAFS and uXANES
X-ray microprobes are widely used in combination with the most modern experimental techniques, such as the X-ray absorption fine structure (XAFS) an X-ray fluorescence analysis (XFA).
The XAFS is generally divided into two parts: into a near-edge region within some 10 eV above an absorption edge and into an extended region well above the edge. The near-edge X-ray absorption fine structure (NEXAFS), also known as X-ray absorption near-edge structure (XANES), requires high-energy resolution (E/DE > 5000) within an energy scan range on the order of 100 eV. The extended X-ray absorption fine structure (EXAFS) consists of relatively weak and broad wiggles, require lower energy resolution within an energy scan range on the order of 1000 eV. Therefore, X-ray polychromatic focusing optics is required to cover the necessary energy range. Capillary X-ray optics has been successfully applied at HZB Adlershof to perform μXAFS measurements with micrometer resolution. Among others the capillary x-ray optical system with a lateral resolution down to 5μm has been used at HZB Adlershof beamlines for:
- the microfocus XAS measurements on volcano-shaped manganese deposits at the cell-wall of the green alga Chara coralline. The evolutionary origin of the manganese complex of oxygenic photosynthesis and possible formation of a bicarbonate precursor complex has been investigated.
- the investigation of oxidation and migration processes of inorganic compounds in ink corroded manuscripts. A model of the ink corrosion mechanism has been suggested based on the experimental results of a combination of μXRF and μ-XANES methods. The influence of restoration treatment on ink corroded manuscripts was carefully investigated.
- the study of glasses containing industrial waste by means of μXRF mapping and μXANES. An inhomogeneous distribution of Fe was observed in the samples. Was also found using μXAS it alteration of the local environment around the Fe atom, which tends to occupy tetrahedral sites in the glass matrix for the regions with low Fe concentration (see figures).