Different Types of XAS techniques
X-ray Absorption Near Edge Structure (XANES) refers to the absorption fine structure close to an absorption edge, about 10 eV below the absorption edge and 20 eV above the edge. This region usually shows the largest variations in the X-ray absorption coefficient and is often dominated by intense, narrow resonances. This part of the spectrum provides information on the electronic structure of the unoccupied levels and the geometry of the studied element - very few techniques can do this.
XANES is also referred to as Near Edge X-Ray Absorption Fine Structure (NEXAFS). Today, the term NEXAFS is typically used for soft X-ray absorption spectra (surface science, organics) and XANES for hard X-ray spectra (coordination chemistry, metal atoms).
EXAFS is the part of XAS spectrum - typically starting ~ 50 eV above the absorption edge. It originates from the scattering of a photoelectron ejected from the absorbing atom and its neighbours. EXAFS is therefore typically used to determine the local structure of the studied element and its surrounding atoms.