Dynamical and kinematical X-ray diffraction in crystals strongly disturbed by ultrasonic vibrations

Abstract

The transition is studied between dynamical and kinematical diffractions, which occurs the amplitude of ultrasound excited in a crystal is increased. The dependences are established of the integrated reflectivity Ri on the amplitude at various relative rates of the acoustic wavelength λs, the extinction length τ, and the crystal thickness T. In the case λs < τ, the initial linear growth of Ri (at |HW| < 1, where H is the diffraction vector, W is the displacement amplitude) changes for the dependence Ri, ∼ |HW|1/2 at 1 ≪ |HW| ≪ (πT/τ)2. In the long wavelength case (τ < λs ≪ T) Ri∼ |HW|2 for |HW| < 1 and Ri< |HW| for 1 ≪ |HW| ≪ (≪/τ)2. If (λ/τ)2≪ ≪ |HW| ≪ (λ/τ)2, the dependence Ri∼|HW|1/2 takes place just as for short wavelengths. And, finally, at |HW| ≫ (πT4τ)2 the integrated reflectivity reaches the kinematical limit for both, short and long waves. The results obtained are applicable to a wide class of deformation fields possessing a characteristic size. [Russian Text Ignored].