Influence of long-range coulombic interactions on binding energy curves of molecule-ions

Abstract

Potential barriers occur on binding energy curves of certain diatomic molecule-ions. The origin of such barriers is discussed for the prototype case consisting of a single electron moving in the field of two nuclei with equal but arbitrary charges. A procedure for determining stationary points on the binding energy curves is developed and applied to the lowest Σ g and Σ u states. The binding energy is expressed as a sum of promotional, coulombic and resonance contributions, and these components are studied as functions of the internuclear distance. The analysis demonstrates that the energy maxima on the Σ g curves arise from long-range coulombic repulsions, and are unrelated to centrifugal potentials of nuclear motion and the mechanisms of predissociation. In addition, the analysis shows that long-range attractions can occur and introduce binding character into normally antibinding states.