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arXiv · 1606.02731

Large enhancement in high-energy photoionization of Fe XVII and missing continuum plasma opacity

Sultana N. Nahar·Anil K. Pradhan
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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 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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Sultana N. Nahar, Anil K. Pradhan. 2016-06-08. Large enhancement in high-energy photoionization of Fe XVII and missing continuum plasma opacity. https://doi.org/10.1103/physrevlett.116.235003

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