Configuration interaction in statistically complete hybrid-structure atomic models

Configuration interaction can have significant effects on the transition energies and strengths of diagnostically important X-ray emission lines and features. However, including full configuration interaction (CI) effects by computing extensive collections of fine structure (LS term) levels may be computationally prohibitive for complex ions. In this paper, we show that CI effects in a simple ion vary little with the configuration of spectator electrons, and that CI effects in complex ions are fairly consistent from one ionization stage to the next, particularly for highly charged ions. Therefore, we argue that the CI effects within an ion can be approximated by extending the CI effects computed from a small subset of configurations in that ion to all transitions of the type (nlj)-(nlj)' in that ion, regardless of the spectator electron. This approach to CI enforces consistency between the fine structure and averaged states in hybrid-structure atomic models, which are designed to provide a computationally efficient balance of spectroscopic accuracy and statistical completeness.