Low-lying valence states of the PO molecule according to configuration-interaction calculations

Abstract

Ab initio configuration-interaction (CI) calculations were carried out for low-lying 2Π, 4Π, 2Σ+, 2Σ−, 4Σ−, 2Δ, and 2Φ valence states of the PO molecule at 11 internuclear distances from 2.45 to 6.5 a.u. All configurations that can be formed from a minimal basis set of Slater-type orbitals, with the restriction of a frozen core, were included. Of the 57 states that dissociate up to 2P(P) + 1S(O), seven 2Π, two 4Π, three 2Σ+, three 2Σ−, one 4Σ−, two 2Δ, and two 2Φ states show a minimum in the potential energy curve. This is to be compared with seven observed valence states.