  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.
