title: Large Enhancement in High-Energy Photoionization of Fe XVII and Missing Continuum Plasma Opacity.
abstract: Aimed at solving the outstanding problem of solar opacity, and radiation transport plasma models in general, we report substantial photoabsorption in the high-energy regime due to atomic core photoexcitations not heretofore considered. In extensive R-matrix calculations of unprecedented complexity for an important iron ion Fe xvii (Fe^{16+}), with a wave function expansion of 99 Fe xviii (Fe^{17+}) LS core states from n≤4 complexes (equivalent to 218 fine structure levels), we find (i) up to orders of magnitude enhancement in background photoionization cross sections, in addition to strongly peaked photo-excitation-of-core resonances not considered in current opacity models, and ii) demonstrate convergence with respect to successive core excitations. The resulting increase in the monochromatic continuum, and 35% in the Rosseland mean opacity, are compared with the "higher-than-predicted" iron opacity measured at the Sandia Z-pinch fusion device at solar interior conditions.
authors.affiliation: Department of Astronomy, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Sultana N
authors.initials: SN
authors.lastname: Nahar
authors.affiliation: Department of Astronomy, The Ohio State University, Columbus, Ohio 43210, USA.
authors.forename: Anil K
authors.initials: AK
authors.lastname: Pradhan