Absolute rate coefficients for photorecombination and electron-impact ionization of magnesium-like iron ions from measurements at a heavy-ion storage ring

TL;DR

This study measures and parametrizes the rate coefficients for photorecombination and electron-impact ionization of Fe$^{14+}$ ions, providing data crucial for modeling astrophysical plasmas, and confirms the agreement with recent theoretical calculations.

Contribution

The paper provides the first experimental measurements of PR and EII rate coefficients for Fe$^{14+}$ ions, with parametrizations for plasma modeling and comparison to theoretical data.

Findings

Experimental rate coefficients agree with theoretical predictions within uncertainties.

Resonance structures in PR and EII are identified and analyzed.

Parametrizations enable practical use in astrophysical plasma modeling.

Abstract

Rate coefficients for photorecombination (PR) and cross sections for electron-impact ionization (EII) of Fe$^{14+}$ forming Fe$^{13+}$ and Fe$^{15+}$, respectively, have been measured by employing the electron-ion merged-beams technique at a heavy-ion storage ring. Rate coefficients for PR and EII of Fe$^{14+}$ ions in a plasma are derived from the experimental measurements. Simple parametrizations of the experimentally derived plasma rate coefficients are provided for use in the modeling of photoionized and collisionally ionized plasmas. In the temperature ranges where Fe$^{14+}$ is expected to form in such plasmas the latest theoretical rate coefficients of Altun et al. [Astron. Astrophys. 474, 1051 (2007)] for PR and of Dere [Astron. Astrophys. 466, 771 (2007)] for EII agree with the experimental results to within the experimental uncertainties. Common features in the PR and EII resonance structures are identified and discussed.