Figure 1
Origin and basic properties of white-beam XAA. (a) Two-atom system: absorbing and scattering atom. The total X-ray field amplitude at the site of an absorbing atom is the coherent sum of an incident plane wave and a scattered spherical wave. In an experiment the orientation of both atoms relative to the incident-beam direction is accomplished by the rotation of the sample. (b) Corresponding X-ray absorption anisotropy . For white X-rays, owing to the short temporal coherence length, anisotropy is significant only at small angles around the interatomic direction. For = 0, owing to a negative value of the X-ray scattering amplitude, there is always a minimum in the absorption anisotropy. |