Analysis of long range dispersion and exchange interactions between two K atoms

This paper critically surveys the best available spectroscopic data for the two lowest electronic states (X ¹Σ_g⁺ and a ³Σ_u⁺) of K₂. Since both states are known up to dissociation, they can be used to determine Coulomb and exchange contributions to the intermediate and long range interaction potentials. The multipolar expansion representation of the Coulomb (dispersion) energy at long range (- Σ_nC_nR^-n) and the exponential representation of the exchange energy (Ae^-αR) as well as a variety of theoretical calculations are compared with these empirical results. Finally, dissociation energy values are discussed and improved dissociation energies for the X ¹Σ_g⁺ (D_e = 4449.1±1.0 cm^-1) and the a ³Σ_u⁺ state (D_e = 252.9±1.1 cm^-1) proposed.