Non-Variational Configuration Interaction Study of Two-Electron and Divalent Atomic Systems

A non-variational configuration interaction (CI) procedure, using a nearly complete set of frozen core Hartree -Fock (FCHF) basis functions constructed from B splines, is applied to the study of the multi-electron interactions in two-electron and divalent atomic systems. Our study has shown that the energy correction due to the continuum contribution to the 3snl ^{1,3 }L series of the Mg isoelectronic sequence, including Al scII, Si scIII, P scIV and S scV, is significant, and that to the 1s^2 ^1S and 2p^2 ^3P^{e } states of H^- is substantial. The configuration interaction between doubly excited bound states and singly excited series has led to the nonuniform variations in quantum defects, oscillator strengths and radiative lifetimes of the Mg isoelectronic sequence. In general, our results are in close agreement with the available experimental data. An extended tabulation of energy levels, oscillator strengths and radiative lifetimes for many bound excited states are presented in this dissertation. A theoretical expression for the effective nuclear charge Z_{eff} is also derived to calculate the fine-structure-level splittings of multiplet states in divalent atoms. Application has been extended to the study of the fine-structure of the ^3P_{J} states of Si scIII. The cancellation between contributions from the 3p3d and 3s5p configurations has led to the J-level inversion in the 3s5p ^3P state of Si scIII. Of the three spin-dependent interaction responsible for the fine-structure-level splittings, the spin-orbit interaction is found to be the dominant one, which contributes approximately 100 times larger than the spin-spin and spin-other-orbit interactions. (Copies available exclusively from Micrographics Department, Doheny Library, USC, Los Angeles, CA 90089-0182.).