Section 4.2.3.3. Normal attenuation coefficients

Fig. 4.2.3.1 shows that the X-ray attenuation coefficients are a smooth function of photon energy over a relatively large range of photon energies, and that discontinuities occur whenever the photon energy corresponds to a resonance in the electron cloud surrounding the nucleus. In Fig. 4.2.3.2, the effect of the interaction of the ejected photoelectron with the electron's neighbouring atoms is shown. Such edge effects (XAFS) can extend 1000 eV from the edge.

It is conventional, however, to extrapolate the smooth curve to the edge value, and a curve of normal attenuation coefficients results. These are taken to be the attenuation coefficients of the individual atoms. Tables of these normal attenuation coefficients are given in Section 4.2.4.