On the Electronic Structure of Electron Doped LaFeAsO1-xFx

We investigated the recently found superconductor LaFeAsO1-xFx by X-ray absorption spectroscopy (XAS). A shift in the chemical potential is visible in both the Fe L-2,L-3 and O K edge spectra which emphasizes the importance of band effects and moderate correlations in these compounds. From experimental Fe L-2,L-3 edge spectra and charge transfer multiplet calculations we gain further information on important physical values such as hopping parameters, the charge transfer energy Delta, and the on-site Hubbard U. Furthermore we find the system to be very covalent with a large amount of ligand holes