Rosseland mean opacities for variable compositions

Abstract

We have undertaken a long-term effort to provide improved Rosseland mean opacity tables. Our earlier work has shown that detailed atomic physics data is crucial to the accurate calculation of opacities. In particular, we showed that the inclusion of LS coupling in the configuration term structure can increase the opacity by factors of 3-4 over the Los Alamos results. Recently, we showed that the additional lines and the shifting of oscillator strength introduced by intermediate coupling can further increase the opacity by as much as 50%. In the present paper we present a method to expand our existing tables to include arbitrary values of hydrogen mass fraction. This task was greatly simplified by showing that there exists a correspondence in the equation of state and opacity for sets of mixtures with the same temperature and electron density, but different mass density and composition. Tables for mixtures of variable hydrogen and metal mass fractions as well as the metal constituents can now be readily calculated.