Ionic oxygen species formed in the presence of lithium, potassium and cesium

Various thick oxidized Li, K and Cs layers have been analysed. The O²⁻, O₂²⁻ and O₂⁻ ions have been characterized through the multiplet structures of their valence-band spectra. Furthermore, the energy separations between the O 1s core levels and the O 2p valence levels were seen to take some given values for each oxygen species. This provides a new way to unambiguously identify these species. In addition, the above energy separations compare rather well to the free ion values, thus allowing discussion on the representation of the oxygen ions which are formed in the presence of alkali metals in terms of a point-charge model.