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Like other absorption spectroscopies, xas techniques follow beer' s law. Exafs is non- destructive, is element specific, and can be applied to samples in the gas, liquid or solid phases. It is employed as a direct probe of the atomic environment of an x- ray absorbing element and provides chemical bonding information. Xafs is commonly divided into the ‘ near edge’ region ( xanes or nexafs) and the ‘ extended’ region ( exafs) mainly single scattering contributions multiple scattering contributions xafs. Extended x- ray absorption fine structure ( exafs ), along with x- ray absorption near edge structure ( xanes ), is a subset of x- ray absorption spectroscopy ( xas ). Exafs is a nondestructive, element- specific spectroscopic technique with appli- cation to all elements from lithium to uranium. If we know these properties, we can determine: r distance to neighboring atom. K- absorption edge of mo metal, showing xanes and exafs regions the equation contains a sum ( taken over all nearest neighboring atoms) of four terms. Exafs xanes or nexas xafs can be interpreted as due to scattering of the photo- electron ejected from the absorbing atom by the photo- electric effect.
2 exafs : extended absorption fine structure spectroscopy exafs is an interference effect caused by the interaction of the outgoing photoelectrons ejected from inner core levels by the resonant radiation, and the backscattered electrons from the near neighbor atoms, modulating the final state wavefunction of the absorbing atom. The exafs equation to model the exafs, we use the exafs equation: ˜ ( k) = x j n jf j( k) e 2r j= ( k) e 2k 2˙ 2 kr j 2 sin[ 2kr j + j( k) ] where f( k) and ( k) are photo- electron scattering properties of the neighboring atom [ and ( k) is the photo- electron mean- free- path].
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