Alkali-metal oxides. II. Unoccupied and excited states

The unoccupied electronic levels of ${\mathrm{NaO}}_2$ and ${\mathrm{KO}}_2$ 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 Xα (LCGTO-Xα) 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.