Generalized electron gas--Drude model theory for ion--molecule forces

A polarized electron-gas theory of intermolecular forces is developed for the case of a spherical ion interacting with a linear molecule. The theory includes, in a unified way, overlap repulsion effects, Coulomb forces, induction effects, and the (small) dispersion forces. Numerical application is made to the cases, Li+--H2 and Li+--N2, and excellent agreement is found with elaborate quantum mechanical calculations for these systems. Comparison with scattering experiments suggests that these measurements correspond to the repulsive potential wall for the orientation of lowest energy, rather than to a uniform average over all orientations