Dynamical theory for calculations of X-ray spectra from crystals modulated by surface acoustic waves

J. Appl. Cryst. (2004). 37, 52–61 [doi:10.1107/S0021889803023847]

Surface acoustic wave (SAW) excitation in the YZ-cut LiNbO₃ causes crystal lattice deformation and leads to “quasi”-waveguide propagation of X-rays in the region under incident beam illumination (see figure). In this region the crystal virtually ceases to reflect despite the fact that the incidence angle is equal to the Bragg angle of the ideal case (perfect crystal). As a consequence, splitting of diffraction peaks on the rocking curve during the experiment are registered. The effect has been explained using direct calculations of the SAW deformation field and simulation of wavefield distribution inside the crystal by numerical integration of the Takagi-Taupin equations. So, the direct problem of X-ray diffraction on a crystal modulated by SAW is believed to be solved.

I. A. Schelokov, D. V. Roshchupkin, D. V. Irzhak and R. Tucoulou