C. Blancard (1), J. Colgan (2), Ph. Cossé (1), G. Faussurier (1), C. J. Fontes (2), F. Gilleron (1), I. Golovkin (3), S. B. Hansen (4*), C. A. Iglesias (5), D. P. Kilcrease (2), J. J. MacFarlane (3), R.M. More (6), J.-C. Pain (1), M. Sherrill (2), and B. G. Wilson (5).
(1) Commissariat a l’Energie Atomique et aux Energies Alternatives, F-91297 Arpajon, France. (2) Los Alamos National Laboratories, Bikini Atoll Road, Los Alamos, NM 87545, USA. (3) Prism Computational Sciences, 455 Science Drive, Suite 140, Madison, WI 53711, USA. (4) Sandia National Laboratories, 1515 Eubank SE, Albuquerque, NM 87185, USA. (5) Lawrence Livermore National Laboratories, P.O. Box 808, Livermore, CA 94550, USA. (6) National Institute for Fusion Science, Toki, Gifu, Japan (ret.)
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.