Chemical shifts in the x-ray emission spectra of MgB2 and their correlation with the electronic structure

The X-ray emission spectra of magnesium diboride MgB2 are measured. It is found that the Mg L(sub 2,3) and B K(sub alpha) emission lines are shifted with respect to the spectra of the pure metals toward the low-energy range. The band calculations of the MgB2 diboride in the framework of the full-potential linearized muffin-tin orbital (LMTO) method demonstrate that the electron populations of the shells in both components of MgB2 are higher than those of pure metals. This increase in the electron populations is associated with the crystal contraction and manifests itself in low-energy shifts of the emission lines.