APPLICATION OF A POINT-CHARGE MODEL TO THE O-2-, O-2(2-) AND O-2(-) IONS FORMED IN THE PRESENCE OF LI, K AND CS

The O2-, O2(2-) and O2- ions which are formed in the presence of Li, K and Cs have been studied by means of XPS and UPS and characterized through the multiplet structures of their valence-band spectra. It has been shown that the binding energies of the electronic levels of these species are consistent with a point-charge model since (i) within experimental errors, core-valence energy separations are independent of the environment and (ii) the experimental values are close to the free-ion values. This work thus opens a new way to identify oxygen species in the presence of alkali metals.