The features of X-ray resonant absorption and scattering, which are the basis of unique methods for studying the electronic, magnetic, phonon, and structural properties of condensed media, are considered. The theoretical description is carried out within the quasi-relativistic approximation of Dirac equation. This makes it possible not only to describe the experimentally observed phe-nomena, but also to predict new spin-position effects in resonance scattering.
78.70.Ck X-ray scattering
11.15.Bt General properties of perturbation theory
31.30.jx Nonrelativistic limits of Dirac-Fock calculations
$^1$Department of Solid State Physics, Faculty of Physics, M.V.Lomonosov Moscow State University.