EFFECT OF THE ADDITIONAL ULTRASOUND DEFOR MATIONS ON THE AMPLITUDE DEPENDENCE OF REFLECTIVITY OF ACOUSTICALLY EXCITED CRYSTAL UNDER CONDITIONS OF X-RAY ACOUSTIC-RESONANCE

The character of the amplitude dependence of the intensity of the Laue -diffracted beams I(W) was experimentally investigated under condition s of the X-ray acoustic resonance at the additional excitation of eith er long-wave or short-wave ultrasonic vibrations in a crystal. Measure ments were carried out on a dislocation-free silicon plates (thickness 9.9 mm) obtained by means of the float-zone method. The reflection 22 0 for the radiation wavelength lambda-0.4 angstrom of the continuous s pectrum was used. It is shown that the behaviour of the obtained curve s I(W) is, on the whole, the same as in the crystals with microdefects , i.e. the dependences are nonmonotonous with the characteristic minim um. The depth of a dip decreases with an increase of the deformation l evel.