R-matrix inner-shell electron-impact excitation of Fe$^{15+}$ including Auger-plus-radiation damping

TL;DR

This study calculates inner-shell electron-impact excitation rates for Fe$^{15+}$ ions using an advanced R-matrix method that includes damping effects, revealing significant reductions in collision strengths compared to previous models.

Contribution

It introduces a comprehensive R-matrix approach with damping for Fe$^{15+}$, improving accuracy over prior calculations that neglected these effects.

Findings

Damping reduces effective collision strengths by 30-40% at low temperatures.

Up to 80% reduction for some transitions due to damping.

Previous calculations overestimated collision strengths by neglecting damping.

Abstract

We present results for the inner-shell electron-impact excitation of Fe$^{15+}$ using the intermediate-coupling frame transformation {\it R}-matrix approach in which Auger-plus-radiation damping has been included. The target and close-coupling expansions are both taken to be the 134 levels belonging to the configurations ${\rm 2s^22p^63}l$, ${\rm 2s^22p^53s3}l$, ${\rm 2s^22p^53p^2}$ and ${\rm 2s^22p^53p3d}$. The comparison of Maxwell-averaged effective collision strengths with and without damping shows that the damping reduction is about 30-40% for many transitions at low temperatures, but up to 80% for a few transitions. As a consequence, the results of previous Dirac $R$-matrix calculations (Aggarwal and Keenan, 2008) overestimate the effective collision strengths due to their omission of Auger-plus-radiation damping.