Abinitiocalculations at the selfhyphen;consistent field and singles plus doubles configurationhyphen;interaction level are used to determine accurate spectroscopic parameters (De,re,ohgr;e) for the2Pgr; and2sum;+states of the alkali oxides and theathinsp;3Pgr; (orAthinsp;1Pgr;) states of the alkalinehyphen;earth oxides. Numerical Hartreendash;Fock (NHF) calculations performed on KO demonstrate that the extended Slater basis sets employed are near the Hartreendash;Fock limit. When the dissociation is referenced to the ionic limits, the differential correlation contribution is found to increase theD0by a relatively small amount (0.0ndash;0.2 eV). An accurate description of the alkali and alkalinehyphen;earth oxides requires correlating both the oxygen and metal electrons. The theoretical dissociation energies (D0) permit a critical assessment of the experimental literature and allow us to recommendD0values that are accurate to 0.1 eV for all systems considered. There is a strong correlation between the dissociation energy (to ions) andre, because the bonding is predominantly electrostatic in origin. Theoretical2Pgr;ndash;2sum;+energy separations are presented for the alkali oxides. An extensive study of the2Pgr;ndash;2sum;+energy separation in KO reveals a2sum;+ground state at all levels of theory. Basis set studies in combination with NHF calculations indicate different basis set requirements for the2Pgr; and2sum;+states. In the NHF limit the2sum;+state of KO is lower by about 250 cmminus;1. The separation is almost unaffected when the 15 valence electrons are correlated at the singles plus doubles level using an extended Slater basis.
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