Nature and properties of x-rays

When x-rays propagate through a substance, the occurrence of the following processes should be considered in the phenomenon of diffraction  

Coherent scattering (section 2.5), which produces beams with the same wavelength as the incident (primary) beam. In other words, the energy of the photons in a coherently scattered beam remains unchanged when compared to that in the primary beam. 

Incoherent (or Compton) scattering, in which the wavelength of the scattered beam increases due to partial loss of photon energy in collisions with core electrons (the Compton effect). 

Absorption of the x-rays, see section 2.3.2.1, in which some photons are dissipated in random directions due to scattering, and some photons lose their energy by ejecting electron(s) from an atom (i.e. ionization) and/or due to the photoelectric effect (i.e. x-ray fluorescence). 

Incoherent scattering is not essential when the interaction of x-rays with crystal lattices is of concern, and it is generally neglected. When absorption becomes significant, it is usually taken into account as a separate effect. Thus, in the first approximation only coherent scattering results in the diffraction from periodic lattices and will be considered in this chapter. 

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