New alternative to the Dunham potential for diatomic molecules

Abstract

A new systematic procedure for constructing potential curves for diatomic molecules is developed. The procedure is similar to the well‐known Dunham method, except that the expansion parameter is (R‐R_e)/R instead of (R‐R_e)/R_e. The new expansion, which has a formal theoretical basis, is shown to be superior in terms of both rate of convergence and region of convergence. It is shown how the expansion coefficients may be obtained from spectroscopic data, and the proper behavior of the potential at large R is shown to allow one to determine additional coefficients and to determine dissociation energies. To illustrate the method, the ground states of hydrogen flouride and carbon monoxide are treated. Possible extensions to polyatomic molecules are briefly discussed.