R-matrix electron-impact excitation data for the N-like iso-electronic sequence

Abstract

Spectral lines from N-like ions can be used to measure the temperature and density of various types of astrophysical plasmas. The atomic databases of astrophysical plasma modelling codes still have room for improvement in their electron-impact excitation data sets for N-like ions, especially $R$-matrix data. This is particularly relevant for future observatories (e.g. Arcus) which will host high-resolution spectrometers. We aim to obtain level-resolved effective collision strengths for all transitions up to $nl=5d$ over a wide range of temperatures for N-like ions from O II to Zn XXIV (i.e., O${}^{+}$ to Zn${}^{23+}$) and to assess the accuracy of the present work. We also examine the impact of our new data on plasma diagnostics by modelling solar observations with CHIANTI. We have carried-out systematic $R$-matrix calculations for N-like ions which included 725 fine-structure target levels in both the configuration interaction target and close-coupling collision expansions. The $R$-matrix intermediate coupling frame transformation method was used to calculate the collision strengths, while the AUTOSTRUCTURE code was used for the atomic structures. We compare the present results for selected ions with those in archival databases and the literature. The comparison covers energy levels, oscillator strengths, and effective collision strengths. We show examples of improved plasma diagnostics when compared to CHIANTI models which use only distorted wave data as well as some which use previous $R$-matrix data. The electron-impact excitation data are archived according to the Atomic Data and Analysis Structure (ADAS) data class it adf04 and will be available in OPEN-ADAS. The data can be used to improve the atomic databases for astrophysical plasma diagnostics.

arXiv commentA&A accepted

References in corpus (10)

• Solar UV and X-Ray Spectral Diagnostics
• CHIANTI - an atomic database for emission lines - Paper XV: Version 9, improvements for the X-ray satellite lines
• Electron impact excitation of OII fine-structure levels
• The Solar Argon Abundance
• Calculations with spectroscopic accuracy: energies and transition rates in the nitrogen isoelectronic sequence from Ar XII to Zn XXIV
• Density diagnostics of ionized outflows in active galactic nuclei: X-ray and UV absorption lines from metastable levels in Be-like to C-like ions
• R-matrix electron-impact excitation data for astrophysically abundant sulphur ions
• Uncertainties on atomic data. A case study: N IV
• R-matrix electron-impact excitation data for the C-like iso-electronic sequence
• Importance of the completeness of the configuration interaction and close coupling expansions in R-matrix calculations for highly-charged ions: electron-impact excitation of Fe ${}^{20+}$

Cited by in corpus (4)

• Quantitative spectroscopy of B-type supergiants
• Quantitative spectroscopy of late O-type main-sequence stars with a hybrid non-LTE method
• R-matrix electron-impact excitation data for the O-like iso-electronic sequence
• Modeling the emission lines from r-process elements in Supernova nebulae