Molecular Constants for l-Uncoupled Electronic States of Diatomic Molecules

Improved methods for the evaluation of the matrix elements in the usual energy expressions for l-uncoupled electronic states of diatomic molecules are discussed. The proposed approximations yield molecular constants which greatly improve the quantitative agreement between theory and experiment. The specific examples of the v = 0 levels of the 3d complexes of BH and He2 are considered in detail. Modifications in the off-diagonal (interaction) elements seem to be the major remaining considerations. Such modifications have only minor effects on the most important of the molecular constants (the electronic energies and B values), however, inclusion of such effects should substantially improve the determination of the higher-order rotational constants.