Temperature-density effects on atomic cross sections in high-energy-density plasmas.

We demonstrate the effects of plasma broadening on R-matrix photoabsorption cross sections and monochromatic opacities as functions of temperature and electron density in astrophysical and laboratory plasmas. In general, all atomic systems are subject to plasma environments, and radiative propagation depends on photoabsorption through bound–bound transitions and autoionizing resonances in bound-free photoionization cross sections. Calculations are carried out for O VI–VII and Fe XVII–XIX. Photoionization cross sections from R-matrix opacity calculations (RMOP) are compared with Opacity Project (OP) data. For selected O VI–VII levels, RMOP cross sections exhibit a much richer resonance structure and extend over broader photon-energy ranges, whereas OP data show no resonances and terminate at lower energies. Monochromatic opacities and Rosseland mean opacities (RMOs) from RMOP are compared directly with OP results under identical plasma conditions. Temperature–density contour plots and broadened cross sections are presented for RMOP.