Forbidden Transitions in the Ground‐State Configuration of Low‐ZPhosphorus‐like Ions

Abstract

Systematically enlarged multiconfiguration Dirac-Fock wave functions have been applied in order to investigate the forbidden lines among the 3s23p3 ground-state levels for phosphorus-like ions at the neutral end of the sequence. The probabilities and ratios of these lines are important in the diagnostics of astrophysical plasmas. In a recent computation by Keenan et al., these probabilities were found to differ by up to ~25% from earlier (partially semiempirical) computations. To analyze this discrepancy in the context of ab initio structure theory, we report on a series of large-scale computations for these magnetic dipole and electric quadrupole transition probabilities. Our computations do not confirm the deviations found by Keenan et al. Detailed comparisons are made with previous calculations and observed data on the separation of energy levels and transition probabilities for the four ions P I, S II, Cl III, and Ar IV. Our study clearly demonstrates the possibility of a systematic approach, but also shows the effort that is needed to obtain sufficiently accurate atomic data for systems with five (or more) valence electrons.