Superposition of Configurations and Atomic Oscillator Strengths—Carbon i and ii

Abstract

Variational wave functions are computed for the ground state and a number of excited states of carbon i and ii by the method of superposition of configurations. To accelerate convergence, the virtual orbitals are obtained from a pseudonatural orbital transformation on a single electron pair, out of all those possible within a given quantum shell. Expansions of up to 50 configurations are generated and used to study the effects of correlation on the oscillator strengths. The method appears to be fairly successful in correcting for most of the correlation error in both the energy and "correlation-sensitive" oscillator strengths. Term values are substantially improved over the Hartree-Fock values; and generally, although not always, $f$ values appear to be obtainable with an accuracy of about 25%.