Configuration interaction calculation of the O2 + ion and study of the photoelectron spectra of O2

Ab initio calculations within the minimal basis of Slater-type orbitals are performed on the O 2 + ion. Full-valence configuration interaction is carried out at seven internuclear separations between 1·0 Å and 2·0 Å. For eight observed bound states, the calculated ordering agrees with experiment, and the root mean square of the differences between the eight calculated and observed vertical excitation energies is 0·45 eV. An analysis of the intensity relations in the photoelectron spectrum of O 2 for ionization of an electron from the 2 σ u or 1 π u molecular orbitals is presented. This leads to a better understanding of some characteristics of these bands and to a new assignment of a few observed peaks.