Long range interaction energies between ground and first excited state hydrogen atoms using a one centre method

Abstract

A one centre method is used to evaluate the long range interaction energies, through O(R -10), between ground and first excited state hydrogen atoms. General pseudo spectral results for both the direct and resonant parts of the expanded second and third order interaction energies are given through any order in R -1. Of particular interest is an O(R -9) third order energy which is totally resonant in character. The advantage of the one centre method for interactions involving degenerate energy states is discussed briefly.