On H2+for small internuclear separation

The author studies the behaviour of the electronic energy E(R) of the hydrogen molecular ion as the internuclear separation R goes to zero. He proves that E(R) is not analytic at R=0 and he finds its expansion in terms of powers of R and R 2 ln R up to order R 9 (ln R) 3 . This rigorously justifies earlier work by Byers Brown and Steiner (1966). He also gives an outline of how one can prove non-analyticity by means of a perturbation treatment based on the united atom.