XPS studies on Ba, BaO and the oxidation of Ba

Abstract XPS investigations on Ba and BaO have been performed to measure characteristic differences between the spectra of Ba and BaO. A typical difference in satellite structure is related to different plasmon losses. The shifts in XPS-peak positions are rather small. However, the X-ray induced Ba (MNN) transition involves, besides differences in plasmon structure a typical change in Auger parameter in going from Ba to BaO. By referring to these characteristics, XPS studies on the oxidation of Ba show a behaviour which may be explained by assuming a continuous transition of Ba into BaO. As far as the XPS data are concerned they do not reveal the presence of an intermediate oxidation state.