Ab initio and semiempirical estimates of PN valence state interactions

Hartree-Fock wavefunctions for the valence states of PN arising from the lowest energy open shell configurations, 2π⁴7σ3π and 2π³7σ²3π, are generated and used in ab initio calculations of diagonal spin-orbit, off-diagonal spin-orbit, and rotation-electronic matrix elements. These results are compared with those from two semiempirical methods, one based on atomic orbital populations and the other dependent solely on atomic spin-orbit splittings. The latter method is found to be surprisingly successful in predicting the ³Δ spin-orbit constant for a series of isovalent molecules. Semiempirical estimates of the ³Δ and ³Π spin-orbit constants of AsN are given. The Hartree-Fock values of the a and b perturbation parameters are found to be 50 cm⁻¹ and 0.60 (unitless), respectively. A previously reported perturbation in the A¹Π-X¹Σ⁺ band system is shown to arise from a ³Σ^{− 1}Π spin-orbit interaction.