Two-electron excitations in atomic calcium. II. Fine-structure effects

A simple recoupling frame transformation is shown to adequately describe numerous effects of the spin-orbit interaction which show up in photoionization of the calcium atom. This is accomplished after solving the nonrelativistic Schr\"odinger equation in LS coupling by an eigenchannel R-matrix method, ignoring all spin-orbit terms in the Hamiltonian. The calculation reproduces most features of the total cross section observed experimentally, and predicts a strong effect of the spin-orbit interaction on partial cross sections, on the photoelectron angular distributions, and on the alignment of the ionic photofragments.