Series Perturbations and Atomic Oscillator Strengths: The D2 Series of Al I

A model calculation has been made of the effects of perturbations of the $3{s}^{2}\mathrm{nd}$ series of aluminum by the $3s3{p}^{2}^{2}D$ term. The model employed is the traditional one of configuration interaction among the independent-particle model representations of the relevant discrete states, with Hartree-Fock functions being used to compute the necessary matrix elements. It is found that, while in the Hartree-Fock approximation the $3s3{p}^{2}$ term is bound and embedded in the $3{s}^{2}\mathrm{nd}$ series, the configuration interaction gives rise to a new autoionizing state just beyond the series limit. This state, which is approximately 50% $3s3{p}^{2}$, is found to have most of the $^{2}D$ absorption oscillator strength ($f=1.1$). The general properties of this model of series perturbations are also discussed in some detail.