Electric Dipole Moment of Diatomic Molecules by Configuration Interaction. III. Open-Shell Molecules CO a3II and CS A 1II

The CI technique developed for closed‐shell molecules is extended to open‐shell cases, retaining a 200 configuration limit, but including higher‐than‐double excitations and employing the iteration to natural orbitals as suggested by Bender and Davidson. For CO the effect of different initial molecular orbitals and different Slater‐type basis sets is examined. For CO a³II, the Hartree—Fock, CI, and experimental dipole moments (in debye) are 2.30, 1.55, and 1.38, respectively. The remaining error in the CI value is attributed more to inadequacies in the Slater‐type basis used than to the CI technique. For CS A¹II the CI dipole moment of 0.63‐D C⁻S⁺ is in excellent agreement with the experimental value of $\text{0.63 ± 0.04}\mathrm{D}$ ; the Hartree—Fock value is 0.09 D in the wrong direction.