Soft-x-ray spectroscopy measurements of the p-like density of states of B in MgB 2 and evidence for surface boron oxides on exposed surfaces

Soft-x-ray absorption and fluorescence measurements are reported for the K edge of B in MgB{sub 2}. The measurements confirm a high density of B p{sub xy}({sigma}) states at the Fermi edge and extending to approximately 0.9 eV above the edge. A strong resonance is observed in elastic scattering through a core exciton derived from out-of-plane p{sub z}({pi}{sup *}) states. Another strong resonance, observed in both elastic and inelastic spectra, is identified as a product of surface boron oxides.