A Quantitative Comparison of Opacities Calculated Using the Distorted- Wave and $\boldsymbol{R}$-Matrix Methods

TL;DR

This paper compares the results of Fe and Ni ion opacities calculated using R-matrix and distorted-wave methods to understand discrepancies and improve the reliability of astrophysical opacity models.

Contribution

It provides a detailed, step-by-step comparison of two main atomic data calculation methods for opacities, highlighting their differences and impacts.

Findings

Differences identified between R-matrix and distorted-wave opacity calculations.

Quantified the effects of configurations and coupling schemes on opacity results.

Enhanced understanding of theoretical uncertainties in astrophysical opacity models.

Abstract

The present debate on the reliability of astrophysical opacities has reached a new climax with the recent measurements of Fe opacities on the Z-machine at the Sandia National Laboratory \citep{Bailey2015}. To understand the differences between theoretical results, on the one hand, and experiments on the other, as well as the differences among the various theoretical results, detailed comparisons are needed. Many ingredients are involved in the calculation of opacities; deconstructing the whole process and comparing the differences at each step are necessary to quantify their importance and impact on the final results. We present here such a comparison using the two main approaches to calculate the required atomic data, the $R$-Matrix and distorted-wave methods, as well as sets of configurations and coupling schemes to quantify the effects on the opacities for the $Fe\ XVII$ and $Ni\ XIV$ ions.