Fine-Structure Studies of Diatomic Molecules: Two-Electron Spin–Spin and Spin–Orbit Integrals

The two-electron integrals that contribute to the spin–spin and spin–orbit interactions in diatomic molecules are evaluated for wavefunctions constructed from Slater orbitals. For arbitrary combinations of quantum numbers, expressions are derived in tensor–operator form for all the one- and two-center Coulomb, hybrid, and exchange terms that occur. An attempt is made in the analysis to maximize compatibility with some of the previous treatments of interelectronic repulsion integrals.