Non-quasiparticle states in the core level spectra of ferromagnetic   semiconductors and half-metallic ferromagnets
  The Green's functions that determine x-ray spectra are calculated in the s-d exchange model of a saturated conducting ferromagnet in the presence of the core hole. A possibility to observe non-quasiparticle (NQP) states in the core level (x-ray absorption, emission and photoelectron) spectroscopy is demonstrated. It is shown that NQP contributions to resonant x-ray scattering spectra can be considerably enhanced by core hole effects in comparison with those to the density of states. 
V. Yu. Irkhin and M. I. Katsnelson