Core Level and Valence Band Studies of the Novel Iron Pnictide Superconductors

Towards understanding the physics of the superconducting iron pnictides, critical information can be gained through exploring the electronic structure of these novel materials. We have used photoemission spectroscopy to study the LaFeAsO$_{1-x}$F$_{x}$ and the PrFeAsO$_{1-x}$F$_{x}$ superconductor. The evolution of valence band density of states, hybridization energy, Fermi surface topology and many body interaction are presented as a function of doping, photon energy and temperature. We explore the significance of these results to the question of electron correlation and spin physics in these Fe-based superconductors.