  We present density functional theory (DFT) calculations and a full set of
X-ray spectra (resonant inelastic X-ray scattering and X-ray photoelectron
spectra) measurements of single crystal CaFe2As2. The experimental valence band
spectra are consistent with our DFT calculations. Both theory and experiment
show that the Fe 3d-states dominate the Fermi level and hybridize with Ca
3d-states. The simple shape of Xray photoelectron (XPS) Fe 2p-core level
spectrum (without any satellite structure typical for correlated systems)
suggests itinerant character of the Fe 3d-electrons. Based on the similarity of
the calculated and experimental Fe 3d-states distribution in LaOFeAs and
CaFe2As2 we conclude that superconductivity in the FeAs-systems can be
described within a minimal model, taking into account only Fe 3d-bands close to
the Fermi level.
