General Relation between Potential Energy and Internuclear Distance for Diatomic Molecules. III. Excited States

A previously proposed internuclear potential function has been used to calculate the dissociation energies for the excited states of a large number of diatomic molecules. From these results and the Wigner-Witmer rules the dissociation products are determined, and it is shown that in many cases it is possible to estimate independently, the dissociation energy of the ground state. The three- and five-parameter forms of the proposed function lead to nearly equal values for dissociation energies suggesting an equivalence of the two forms. This leads to a relation between the anharmonicity and the vibrational-rotational coupling constant which is slightly superior to the Pekeris relation. Equations derived from this relation are given relating the parameters a and b of the five-parameter functions to the anharmonicity or vibrational-rotational coupling constant. The parameter b and to a lesser extent a was found nearly constant for the excited states of all diatomic molecules.