Spectroscopic diagnostics of low-ionized iron-peak elements. Electron-impact excitation of Ni$^{3+}$ and photoionisation of Ni$^{2+}$

TL;DR

This paper provides detailed atomic data for Ni IV and Ni II ions, improving plasma diagnostics by calculating electron-impact excitation and photoionisation rates crucial for astrophysical spectral analysis.

Contribution

It introduces advanced R-matrix calculations for Ni$^{3+}$ and Ni$^{2+}$, offering new, accurate atomic data for low-ionized iron-peak elements used in astrophysical diagnostics.

Findings

Generated high-quality excitation and ionisation data sets.

Calculated line ratios for plasma temperature and density diagnostics.

Enhanced understanding of Ni-peak element spectra in astrophysics.

Abstract

The spectra from Fe-peak elements may be used to determine the temperature and density of various astrophysical objects. Determination of these quantities is underpinned by the accuracy and the comprehensiveness of the underlying atomic structure and collisional calculations. In the following paper, we shall focus specifically on Ni IV lines associated with transitions amongst several low-lying levels. We shall employ modified versions of the parallel Dirac R-matrix codes, considering both electron-impact excitation of Ni$^{3+}$ and the photoionisation of both the ground and excited states of Ni$^{2+}$. We produce high-quality data sets for both processes, and using these data, we calculate line ratios relevant for plasma diagnostics of temperature and density.