The Opacity Project: R-Matrix Calculations for Plasma Opacities

In a series of 4 papers entitled "R-matrix calculations for opacities" (RMOP), following the Opacity Project work, an extended version of the R-matrix methodology is presented for calculation of improved astrophysical and laboratory plasma opacities. Contrast and comparisons with existing methods primarily relying on the Distorted Wave (DW) approximation are discussed. Among the improvements incorporated are: (I) large-scale Breit-Pauli R-matrix (BPRM) calculations for complex atomic systems including fine structure, (II) convergent close coupling wave function expansions for the (electron+ion) system to compute oscillator strengths and photoionization cross sections of open and closed shell iron ions of interest in astrophysics and experiments, (iii) a new treatment for plasma broadening of autoionizing resonances as function of energy-temperature-density dependent cross sections including collsiional, Stark and thermal effects, and (iv) convergences, completeness and comparison of RMOP and DW opacities. Also implemented are a "top-up" procedure to compare convergence with R-matrix calculations for highly excited levels, and spectroscopic identification of resonances and bound (e+ion) levels obtained from ab inito R-matrix calculations. Based on the present work, opacities of heavy elements might require revisions in high-energy-density plasma sources. Interface of the equation-of-state, atomic data, and opacities is examined with reference to experimental measurements of opacities.