Electron distribution in MgO probed by x-ray emission

The relative intensity of the Mg Kβ emission band with respect to the Kα atomic line, obtained by electron-induced x-ray emission spectroscopy, is used to investigate the variation of p-like valence electron number located around magnesium in metal and MgO. Calculated spectral intensities of Mg K emissions are obtained within the augmented plane-wave method for the perfect crystal. From experimental and theoretical data, the number of $3p$ electrons present around Mg and involved in the Kβ transition does not vary much with the metallic or ionic character of the bonds. This result shows that the charge transfer is weak in the oxide. These experiments can be generalized to other compounds. Spectral densities of states (DOS) around Mg and O are also probed and agreement is found between experimental and theoretical spectral densities of $3p$ Mg and $2p$ O states. Changes of MgO valence DOS with annealing, etching, and aging are discussed.