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[en] Using Geant4 toolkit, the differential cross-section and the atomic form factor for coherent scattering of 25.2 heV photons in some tissue - equivalent compounds at 90 degree were calcuated. The results gave good agreement with those calculated theoretically. (author).
[en] The mechanism of suppression of inelastic channels that is not associated with the Bragg diffraction in a three-dimensional lattice, is investigated for a two-dimensional model. For the purpose coherent scattering on a monoatomic crystal film is considered with account of mutual irradiation of the lattice points by scattered radiation. The same problem is considered simultaneously on the basis of the optical theorem modification for a plane lattice formulated in the paper. As a result, the generic formula expressing the plane scattering amplitude q0 in terms of an individual free node amplitude is obtained along with the expression for the variation of free amplitude f0 → tilde f0 in the points concentrating in the lattice. The relations allow one to predict a sharp growth of the coefficient of reflection from one atomic plane at incident radiation frequencies close to the resonance atomic frequencies. In the presence of inelastic channels the effect of their suppression is possible due to which a two-dimensional crystal may elastically reflect backward almost all the radiation, although the same radiation is absorbed almost completely in the process of scattering on an isolated lattice point. The relationship between the resonance reflection line width and band structure of a two-dimensional crystal is found. The possibility of the effect observation is discussed
[en] Neutron scattering formalism is briefly surveyed. Topics touched upon include coherent and incoherent scattering, bound and free cross-sections, the Van Hove formalism, magnetic scattering, elastic scattering, the static approximation, sum rules, small angle scattering, inelastic scattering, thermal diffuse scattering, quasielastic scattering, and neutron optics