SEARCH Articles Figures Tables First-Order Spin-Orbit Coupling First-Order Spin-Orbit Coupling Selection Rules First-order Zeeman splitting orbitals First-order spin-orbit perturbation First-order spin-orbit splitting Mixing of Degenerate Orbitals— First-Order Perturbations Molecular orbital first-order Orbital order Orbitally ordered Relativistic corrections first-order spin-orbit correction from Spin-orbit interaction, first-order Spin-orbital representation, with first-order