DIFFRACTION OF X-RAYS AT THE FAR TAILS OF THE BRAGG PEAKS .2. DARWIN DYNAMICAL THEORY

The Darwin theory of dynamical diffraction by crystals is extended to include the regions between Bragg peaks as well as situations of grazi ng and normal angles of incidence, i.e., the whole angular range exten ding from 0-degrees to 90-degrees. The modified theory reproduces the usual two-beam Laue dynamical theory in the close vicinity of the Brag g peaks, while in the regions between the Bragg peaks it predicts refl ectivities in agreement with the kinematical theory. Many-beam effects due to all crystallographic planes parallel to the surface can be cal culated in an extremely simple way making this approach particularly s uitable to artificial multilayered structures. The weak scattering in the region where the far tails of two neighboring Bragg peaks interfer e contains information about the phases of the structure factors.