Electronic structure of the lowest¹,³Σ⁺g,¹,³Σ⁺u,¹,³Πg,¹,³Πu,¹,³Δgand¹,³Δustates of K₂from valence CI calculations

The authors have calculated the potential energy curves for the molecular states of K 2 dissociating to K(4s+4s), K(4s+4p), K(4s+5s) and K(4s+3d), using a Hartree-Fock pseudopotential method to describe the alkali core, followed by a configuration interaction computation. Comparison is made with experimentally determined potential curves and with other theoretical results. The core-valence interactions in the potassium atom are investigated through an all-electron calculation, and an improved set of excitation energies to be used to obtain London-type dispersion terms is proposed. The electron distributions in the high-lying valence states and Rydberg states of K 2 and Na 2 are analysed and compared.