D Gilles1, M Busquet2, F Gilleron3, M Klapisch4 and J-C Pain3
1 CEA, DSM, IRFU, F-91191 Gif-sur-Yvette, Cedex, France, 2 Research Support Instruments, Lanham, MD 20706, USA, 3 CEA, DAM, DIF, F-91297 Arpajon, France, 4 Berkeley Research Associates, Beltsville, MD 21042, USA
We have recently shown that iron and nickel open M-shell opacity spectra, up to Δn = 2 are very sensitive to Configuration Interaction (CI) treatments at temperature around 15 eV and for various densities. To do so we had compared extensive CI calculations obtained with two opacity codes HULLAC-v9 and SCO-RCG. In this work we extend these comparisons to a first evaluation of CI effects on Rosseland and Planck means.
Influence of the number of atomic levels on the spectral opacity of low temperature nickel and iron in the spectral range 50-300 eV
M. Busquet, M. Klapisch, and D. Gilles
Opacity is a fundamental ingredient for the secular evolution of stars. The calculation of the stellar plasma absorption coefficients is complex due to the composition of these plasmas, generally an H /He dominated mixture with a low concentration of partially ionized heavy ions (the iron group). The international collaboration OPAC recently presented extensive comparisons of spectral opacities of iron and nickel for temperatures between 15 and 40 eV and for densities of ˜ 3 mg/cm3, relevant to the stellar envelope conditions [1, 2]. The role of Configuration Interaction (CI) and the influence of the number of atomic levels on the opacity using the recently improved version of HULLAC atomic code [3, 4] are illustrated in this article. Comparisons with theoretical predictions already presented in  are discussed.