Effects of Configuration Interaction on 3s Shell Photoionization in Argon Atoms

This study systematically investigates the effects of configuration interaction (CI) on the photoionization of the 3s shell in argon atoms using relativistic multiconfiguration Dirac–Fock methods. To quantify both CI effects and electron correlations, four distinct computational models were employed: Model A (single-configuration), Model B (restricted configuration with valence excitations up to the 4p orbital), Model C (extended configuration with core–valence excitations up to the 4p orbital), and Model D (extended configuration with core–valence excitation up to the 4d orbital). The results demonstrate that Models C and D, which incorporate single and double excitations from core–valence electrons into the 4p and 4d orbitals, achieve excellent agreement with the experimental cross-sectional data. Notably, the angular asymmetry-parameter β exhibits pronounced energy-dependent behavior, with significant divergence observed between models employing restricted versus extended CI treatments. A detailed analysis was conducted to explore the variations in boundstate and continuum-state electron orbitals across different models, as well as their influence on the photoionization transition matrix elements. This work underscores the critical importance of accurately modeling core– valence electron correlations for reproducing both absolute cross sections and photoelectron angular distributions, particularly near ionization thresholds and the Cooper minimum. These findings provide valuable insights into the fundamental mechanisms governing photoionization processes and highlight the need for advanced theoretical frameworks to enable precise predictions in atomic collision dynamics.

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