Calculation of Spin-Orbit Coupling Constants in Diatomic Molecules from Hartree-Fock Wave Functions

Spin-orbit coupling constants are calculated from Hartree-Fock wave functions of diatomic molecules using the Dirac Hamiltonian. For first-row diatomic hydrides, agreement with experiment is good (∼5%) provided that two-electron integrals are considered. These two-electron integrals may be interpreted as providing a shielding of the nuclear charge; they reduce the computed value of the coupling constant from that found from simple $\frac{Z}{{\mathcal{r}}^3}$ terms. The applications to ${}_{}{}^2{}_{}{}^{}\mathrm{II}$ states of BeH, CH, and OH are specifically considered.