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

TL;DR

This paper critically evaluates recent R-matrix calculations claiming to significantly enhance Fe XVII opacity, showing that standard models already match or exceed these results and do not resolve existing experimental-theoretical discrepancies.

Contribution

It demonstrates that the recent R-matrix results do not provide a substantial improvement over standard opacity models in explaining experimental data.

Findings

Standard models match or exceed the R-matrix opacity results.

R-matrix calculations do not resolve the missing continuum plasma opacity issue.

No significant enhancement in Fe XVII opacity from recent R-matrix work.

Abstract

Recent R-matrix calculations claim to produce a significant enhancement in the opacity of Fe XVII due to atomic core excitations [S. N. Nahar & A.K. Pradhan, Phys. Rev. Letters 116, 235003 (2016), arXiv:1606.02731] and assert that this enhancement is consistent with recent measurements of higher-than-predicted iron opacities [J. E. Bailey et al., Nature 517, 56 (2015)]. This comment shows that the standard opacity models which have already been directly compared with experimental data produce photon absorption cross-sections for Fe XVII that are effectively equivalent to (and in fact larger than) the new R-matrix opacities. Thus, the new R-matrix results cannot be expected to significantly impact the existing discrepancies between theory and experiment because they produce neither a "large enhancement" nor account for "missing continuum plasma opacity" relative to standard models.