A large-scale R-matrix calculation for electron-impact excitation of the Ne$^{2+}$ O-like ion

TL;DR

This paper presents extensive R-matrix calculations for electron-impact excitation of Ne$^{2+}$ O-like ion, improving atomic data accuracy and providing new diagnostics for astrophysical plasma analysis.

Contribution

It introduces a large-scale 554-level ICFT R-matrix calculation that extends previous data, offering comprehensive excitation data for astrophysical diagnostics.

Findings

Provides a comprehensive dataset of electron-impact excitation rates.

Improves accuracy of line ratio predictions at low temperatures.

Enhances diagnostic capabilities for astrophysical observations.

Abstract

The five J$\Pi$ levels within a $np^2$ or $np^4$ ground state complex provide an excellent testing ground for the comparison of theoretical line ratios with astrophysically observed values, in addition to providing valuable electron temperature and density diagnostics. The low temperature nature of the line ratios ensure that the theoretically derived values are sensitive to the underlying atomic structure and electron-impact excitation rates. Previous R-matrix calculations for the Ne$^{2+}$ O-like ion exhibit large spurious structure in the cross sections at higher electron energies, which may affect Maxwellian averaged rates even at low temperatures. Furthermore, there is an absence of comprehensive excitation data between the excited states that may provide newer diagnostics to compliment the more established lines discussed in this paper. To resolve these issues, we present both a small scale 56-level Breit-Pauli (BP) calculation and a large-scale 554 levels R-matrix Intermediate Coupling Frame Transformation (ICFT) calculation that extends the scope and validity of earlier JAJOM calculations both in terms of the atomic structure and scattering cross sections. Our results provide a comprehensive electron-impact excitation data set for all transitions to higher $n$ shells. The fundamental atomic data for this O-like ion is subsequently used within a collisional radiative framework to provide the line ratios across a range of electron temperatures and densities of interest in astrophysical observations.