Teoria semi-cinemática da difração de raios X moles em cristais

Abstract

The soft x-ray diffraction techniques were only recently explored with the advent of 3rd generation synchrotrons. In this energy range, the crystals are strongly absorbing, and the measured intensity can be described by the particular case of thick crystals. However, a simple and general description for crystals of any thickness is missing. In this work, a theory of soft x-ray diffraction in strongly absorbing crystals of any thickness was analytically developed based on semi-kinematical treatment, in which linear absorption and refraction are considered, and primary extinction is neglected. It is a special case for the semi-kinematical approximation of Laue dynamical theory. For thick crystal, the diffracted intensity has a Lorentzian shape, with the full width at half maximum proportional to the linear absorption coefficient, being in accordance with the analysis methods used in the technique of Resonant Soft X-ray Scattering (RSXS). For crystals of any thickness, the integral breadth was obtained as a function of thickness, of which the Scherrer equation is a particular case, and differing from the expression for primary extinction only by the attenuation quantifier. Applications in RSXS are discussed for finite and thick crystals. This work describes the soft x-ray diffraction in crystals.