Alkali-metal oxides. II. Unoccupied and excited states

The unoccupied electronic levels of NaO2 and KO2 have been probed by inverse photoemission. In addition, excitation spectra of various core and valence levels have been recorded with use of x-ray absorption spectroscopy and electron-energy-loss spectroscopy. Results from a linear combination of Gaussian-type orbitals X (LCGTO-X) model cluster study and photoemission data previously reported give a coherent and detailed description of ground- and excited-state properties of the alkali-metal superoxides. This description includes molecular and crystal-field effects, excitonic properties of the excited states, and electron-hole correlation energies as well as transition-matrix-element effects.