X-ray Absorption Fine Structure (XAFS)
The XAFS technique provides information about the atomic structure in
the immediate vicinity of an x-ray absorbing atom. The photoelectron which
is emitted following absorption, may be thought of as a wave.
This wave interacts with the atoms which surround the absorbing atom.
The result of this interaction is modulation of the absorption spectrum
at energies higher than the absorption edge.
Deconvolution of these modulations provides information on the number,
type and distance of near neighbours. XAFS can be applied to materials of
any phase crystalline, non-crystalline solid, solution, or gas. Also,
the fine structure appearing close to the absorption edge gives further
information (XANES).
Example of EXAFS analysis on copper acetate:
The position of a peak gives information about the interatomic distance,
its width gives information about the movement of defect atoms.
Peak height contains information about the number of neighbouring
atoms around each copper atom. Copper (II) acetate form dimers
in the solid but exist as a monomers in aqueous solution.
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