NEXAFS experiment and multiple scattering calculations on KO2: Effects on the pi resonance in the solid phase

The high-energy resolution O K-edge absorption near-edge x-ray absorption fine structure 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 the rising edge, which presents a double-peak 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 1.31 and 1.34 Angstrom. Moreover, the calculation demonstrates both a complete ionic character of the bound between the O2- anion and K atoms and a strong interaction between the anion and solid-state matrices.