  The Fe K X-ray absorption near edge structure (XANES) of BaFe2-xCoxAs2
superconductors was investigated. No appreciable alteration in shape or energy
position of this edge was observed with Co substitution. This result provides
experimental support to previous ab initio calculations in which the extra Co
electron is concentrated at the substitute site and do not change the
electronic occupation of the Fe ions. Superconductivity may emerge due to
bonding modifications induced by the substitute atom that weakens the
spin-density-wave ground state by reducing the Fe local moments and/or
increasing the elastic energy penalty of the accompanying orthorhombic
distortion.
