CNR, ISM, Trieste, Italy
; Ist Nazl Fis Nucl, Lab Nazl Frascati, I-00044 Frascati, Italy
; Univ Autonoma Madrid, Madrid, Spain
; CNR, IMAI, Trieste, Italy
; Chinese Acad Sci, Inst High Energy Phys, Beijing Synchrotron Radiat Facil, Beijing 100039, Peoples R China
Article; Proceedings Paper
Since many years the oxidation of alkali metals has being attracted much interest due to the catalytic properties of metal promoters and the simple electronic structure of alkali atoms. The alkali-oxides phase diagram indicates that the interaction of oxygen with alkali metals can lead to the formation of different atomic O2- ions and molecular O-2(-) and O-2(2-) ions. Potassium superoxide has been prepared in situ and high resolution O k-edge absorption NEXAFS spectra have been measured at the VUV beam-line at ELETTRA facility. The experimental data have been analyzed by multiple scattering approach deriving many geometrical and electronic details. In particular, we have found that the growth material structure is of the KO2 type with an O-O distance of about 1.35 Angstrom and that the transition involving single pi molecular empty state of the superoxide O-2(-) anion has a fine structure. Multiple Scattering self consistent calculation indicates that the bond between oxygen anion and K atom is totally ionic and that the fine structure is essentially due to solid state effects.