Key points are not available for this paper at this time.
The valence-band structures of MnO, CoO, NiO, Cu₂O, CuO, and ReO₃ have been obtained by x-ray photoemission spectroscopy. It is found that in every case a narrow metal d band lies above the center of the oxygen 2p valence band.
Wertheim et al. (Mon,) studied this question.