XAS: X-ray Absorption Spectroscopy

A range of X-ray Absorption Spectroscopy techniques are available at Diamond, including X-ray Absorption Near-Edge Structure (XANES), Extended X-ray Absorption Fine Structure (EXAFS), Resonant Inelastic X-ray Scattering (RIXS) and X-ray Emission Spectroscopy (XES).

At characteristic wavelengths the X-ray absorption of an element changes dramatically, these are called absorption edges. Near the absorption edge, the spectra may contain fine structure that reveals the electronic and geometrical environment of the absorbing atom. This technique is XANES; further from the edge EXAFS reveals the local atomic environment to the element. Both can be used to can follow reactions on timescales down to the millisecond.

The high intensity of synchrotron X-rays make it possible to detect elements present in very low concentrations. The tuneability of synchrotron radiation allows XAS spectra of virtually all the elements to be collected in short time periods. Combining the high brightness with the small spot size available makes it possible to examine samples with very high spatial resolution.

X-ray absorption spectroscopy is important in gaining structural understanding of a range of materials, including biomaterials, novel materials with special electronic properties such as superconductivity, dilute species in fluids, and complex inhomogeneous materials. It can provide information on bio-remediation processes, study minute minerals returned from space missions and be used to understand chemical reactions such as heterogeneous catalysis and hydrothermal synthesis of industrial materials.

microXAS is a subset of XAS, where XAS measurements are carried out on a micron-size spatial scale. To do this a small beam is obtained using focusing optics as opposed to larger beam sizes used during regular XAS.