STUDIES OF PROCESSES OF DIFFRACTION OF HIGH-MONOCHROMATIC GAMMA-RADIATION IN REAL SINGLE CRYSTALS. Alexander Kurbakov, Alexei Sokolov, Department of Condensed Matter, Petersburg Nuclear Physics Institute, 188350, Gatchina, Russia

Diffraction of high-monochromatic short-wavelength (0.003nm) gamma- radiation was used to experimental study of diffraction process in real single crystals.

To check-up the modern theoretical elaborations in the field of creation of the general theory of diffraction , in additional to recent gamma-ray and X- ray experimental tests of Kato's statistical dynamical theory by measuring the period of the intensity beats and values of integral intensities as a function of the sample thickness or wavelength that can be applied only to highly perfect crystals, we carried out experiments on both quite perfect crystals and crystals with relatively high distortions of the crystal lattice formed during crystal growth and/or different technological operations. It was used dislocationless Si and Ge single crystals, Si undergone special purposeful influences to their crystal structure and Ge after plastic deformation. Also we investigated single crystals of quartz, which as Si has rather high degree of structure perfection, but principally different, from point of influence to diffraction process, low-dislocation defect structure. Mainly it was used the possibility of measuring the absolute values of integral reflecting power in the condition of a high angular resolution for several orders of reflection (hkl).

So we had possibilities to realise the conditions for changing the values of static Debye-Waller factor E in all range from 1 to 0 and measuring the dependencies of E upon reflection vector for various types of lattice defects.

A detailed discussion of the applicability of Kato's statistical dynamical theory (with account of last theoretical elaborations) and other modern theories to short-wavelength gamma-ray diffraction experimental data are given.