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

This paper critically surveys the best available data for the two lowest states (X 1Σ+g and a 3Σ+u) of Na2. Since both states are known up to near dissociation, they can be used to determine the separate Coulomb and exchange contributions to the intermediate and long range interaction potentials. The multipolar expansion representation of the Coulomb (dispersion) energy at long range (−∑nCn/Rn) and the exponential representation of the exchange energy at long range (Ae−aR) are tested.