Photoelectron interference process, EXAFS

Figure 4. The fundamental photoelectron interference process in EXAFS...

FIGURE 2.23 The EXAFS process (a) the photoelectron is ejected by X-ray absorption, (b) the outgoing photoelectron wave (solid line) is backscattered constructively by the surrounding atoms (dashed line), and (c) destructive interference between the outgoing and the backscattered wave. 

Figure 2.13 A schematic representation of the EXAFS process. An atom (filled circle) absorbs X-rays, emitting a photoelectron wave which is back-scattered by neighbouring atoms (hatched circles). The solid circles denote outgoing electron waves and the broken circles back-scattered electron waves. Constructive or destructive interference can occur when the waves overlap.

Fig. 8. In EXAFS, the absorption of X-ray radiation is determined as a function of photon energy. The photoelectrons generated in the photoabsorption process at an adsorbate-atom are backscattered from substrate atoms and lead to modulation of the absorption cross section through interference phenomena. In the center figure the lines of equal phase of the backscattered radiation go through the excited atom (see top) resulting in constructive interference, whereas in the bottom figure the photoelectron kinetic energy is slightly different, resulting in destructive interference at the position of the excited atom.

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