Statistical theory of diffraction of X-ray and light waves in periodic substances

A consistent theory of dynamical diffraction of X-ray and light waves from two-dimensional crystals with statistically distributed defects has been developed. The influence of disorder in the scatterer arrangement on the properties of a coherent wave field is analyzed for the case of Laue diffraction with due regard for the second momenta of a fluctuating, field distribution. The analytical expressions for the coherence length of electromagnetic fields under diffraction conditions are derived. It is shown that, under the conditions of dynamical diffraction, two Bloch waves with different absorption coefficients are generated in an initially nonabsorbing crystal with defects. The antinodes of the weakly absorbed wave are located in the region between the scatterers, whereas the antinodes of the strongly absorbed wave coincide with the equilibrium scatterer positions. (C) 2004 MAIK "Nauka/Interperiodica".