The influence of core–valence electron correlations on the convergence of energylevels and oscillator strengths of ions with an open 3d shell using Fe VIII as anexample

Abstract

Accurate atomic data, such as fine structure energy levels and oscillator strengthsof different ionization stages of iron ions, are important for astrophysical andlaboratory plasmas. However, some important existing oscillator strengths for ionswith an open 3d shell found in the literature might not be accurate enoughfor practical applications. As an example, the present paper checks theconvergence behaviour of the energy levels and oscillator strengths of Fe VIII bysystematically increasing the 3pn–3dn(n = 1, 2, 3and 6) core–valence electron correlations using the multiconfiguration Hartree–Fockmethod. The results show that one should at least include up to 3p3–3d3core–valence electron correlations to obtain converged results. Large differencesare found between the present oscillator strengths and other theoretical results inthe literature for some strong transitions.