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 photo-excitations 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 $n leq 4$ 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.
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