Uncertainties on atomic data. A case study: N IV
Abstract
We consider three recent largescale calculations for the radiative and electronimpact excitation data of N IV, carried out with different methods and codes. The scattering calculations employed the relativistic Dirac Rmatrix (DARC) method, the intermediate coupling frame transformation (ICFT) Rmatrix method, and the Bspline Rmatrix (BSR) method. These are all largescale scattering calculations with welltested and sophisticated codes, which use the same set of target states. One concern raised in previous literature is related to the increasingly large discrepancies in the effective collision strengths between the three sets of calculations for increasingly weak and/or highlying transitions. We have built three model ions and calculated the intensities of all the main spectral lines in this ion. We have found that, despite such large differences, excellent agreement (to within ±20 per cent) exists between all the spectroscopically relevant line intensities. This provides confidence in the reliability of the calculations for plasma diagnostics. We have used the differences in the radiative and excitation rates amongst the three sets of calculations to obtain a measure of the uncertainty in each rate. Using a Monte Carlo approach, we have shown how these uncertainties affect the main theoretical ratios that are used to measure electron densities and temperatures.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 April 2019
 DOI:
 10.1093/mnras/stz206
 arXiv:
 arXiv:1901.08450
 Bibcode:
 2019MNRAS.484.4754D
 Keywords:

 atomic data;
 techniques: spectroscopic;
 Astrophysics  Solar and Stellar Astrophysics;
 Physics  Atomic Physics
 EPrint:
 Accepted for publication