Many-body calculations of atomic properties. I. gjfactors

Many-body perturbation theory has been applied to compute expectation values of the one- and two-electron interactions which yield the relativistic corrections (Abragam-Van Vleck terms) to the atomic g J factors. A two-electron term due to the motion of the atomic nucleus is also considered. The present calculations are based on analytic expansions of the single-particle states, and a main purpose of the work is to investigate the capability of this method for computations of complex atomic properties. The examples considered are the ground states of the alkali atoms up to rubidium, the ground states of the first-row atoms, and chlorine. The calculations are complete to third order and some fourth-order diagrams are also included. For the first-row atoms energy lowerings ranging from 82-92% of the experimental correlation energies were obtained, showing that a considerable amount of correlation has been included. The computed g J factors are compared with high-precision experimental values and reasonable agreements for the troublesome cases of nitrogen and the fluorine 2 P 1/2 state are among the present achievements. Correlation effects were in several cases found to be of importance for the computed g J factors.