Plasma diagnostic potential of 2p4f in N$^+$ -- accurate wavelengths and oscillator strengths

TL;DR

This paper provides high-precision wavelengths and oscillator strengths for 2p4f transitions in N$^+$, aiding nebulae plasma diagnostics and abundance measurements by systematically including relativistic effects.

Contribution

The study introduces accurate calculations of wavelengths and oscillator strengths for N$^+$ 2p4f transitions using the multiconfiguration Dirac-Hartree-Fock method, accounting for relativistic effects.

Findings

Uncertainties controlled within 3% for wavelengths and 5% for oscillator strengths.

Relativistic effects significantly impact the accuracy of transition data.

Comparison shows discrepancies with previous non-relativistic calculations.

Abstract

Radiative emission lines from nitrogen and its ions are often observed in nebulae spectra, where the N$^{2+}$ abundance can be inferred from lines of the 2p4f configuration. In addition, intensity ratios between lines of the 2p3p -- 2p3s and 2p4f -- 2p3d transition arrays can serve as temperature diagnostics. To aid abundance determinations and plasma diagnostics, wavelengths and oscillator strengths were calculated with high-precision for electric-dipole (E1) transitions from levels in the 2p4f configuration of N$^{+}$. Electron correlation and relativistic effects, including the Breit interaction, were systematically taken into account within the framework of the multiconfiguration Dirac-Hartree-Fock (MCDHF) method. Except for the 2p4f - 2p4d transitions with quite large wavelengths and the two-electron-one-photon 2p4f -2s2p$^3$ transitions, the uncertainties of the present calculations were controlled to within 3% and 5% for wavelengths and oscillator strengths, respectively. We also compared our results with other theoretical and experimental values when available. Discrepancies were found between our calculations and previous calculations due to the neglect of relativistic effects in the latter.