Neutron reflectivity of perfect crystals excited by high-frequency ultrasound

Neutron scattering double-crystal experiments were realized using high-frequency ultrasonic excitation in a perfect silicon single crystal. The dependence of rocking curves on the ultrasonic amplitude was measured and compared with the dynamical theory. It was found that the method of the transfer matrix is very useful for the analysis of the influence of the acoustic wave (AW) on the diffraction in very thick crystals. In particular, the pendellösung oscillations are simply and exactly removed from the whole picture of the diffraction pattern. Some exact theoretical conclusions concerning the maximum influence of ultrasound and the deformation at the peak intensity in a double-crystal spectrometer were also reviewed.