SEARCH Articles Figures Tables First-order spin-orbit perturbation Orbital perturbation Orbital perturbed Orbitals perturbations Perturbation theory applied to spin-orbit coupling Perturbational Approaches to Spin-Orbit Coupling Spin-orbit coupling perturbation theory Spin-orbit coupling perturbative handling Spin-orbit interaction perturbation Spin-orbit interaction perturbation theory Spin-orbit perturbation matrix elements Spin-orbit perturbed wave functions Spin-orbital perturbed