NEXAFS Experiment and Multiple Scattering Calculations on KO2: effects on the phi resonance in the solid phase

The high-energy resolution O K-edge absorption NEXAFS spectrum has been measured for in situ prepared potassium superoxide. The experimental data have been analyzed in detail by multiple scattering calculations using self-consistent field potentials. In particular the so-called pi resonance at rising edge, which presents a double peaks structure, has been totally resolved and reproduced by the calculations. This analysis indicates that the grown material is arranged in a KO2 structure with an O-O distance between 1.31Å and 1.34Å. Moreover, the calculation demonstrates both a complete ionic character of the bound between the O2- anion and the K atoms and a strong interaction between the anion and the solid-state matrices.