Use of Green Functions in Atomic and Molecular Calculations. III. Second-Order Perturbation of the Hydrogen Molecular Ion

We have derived analytical expressions for the second‐order perturbation energy of a hydrogen atom, perturbed by a point charge $\lambda$ at a distance $R$ . Here the charge $\lambda$ is taken as the perturbation parameter. The calculations make use of Green‐function techniques and of the hydrogen‐atom Green function that we derived in a previous publication.