Benchmarking atomic data for astrophysics: ^*,**

¹ Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, UK e-mail: G.Del-Zanna@damtp.cam.ac.uk
² School of Science and Mathematics, Sheffield Hallam University, Sheffield S1 1WB, UK

Received: 2 October 2003
Accepted: 7 April 2004

Abstract

This is the first in a series of papers in which we benchmark recent atomic data available for astrophysical applications. We review various issues related to the completeness and accuracy of both theoretical and experimental data. In this paper, the available experimental and atomic data for ( configurations) are reviewed and assessed. New collisional and radiative data are calculated to supplement published data. The radiative calculations are done with empirical adjustements that take into account observed wavelengths. Previous line identifications are also reviewed and assessed. Our approach focuses on the brightest spectral lines, and uses both wavelengths and line intensities to assess the line identifications on a quantitative basis. Although many previous line identifications are confirmed, some are rejected (e.g. the coronal line observed at 1582.35 Å). We confirm previously suggested identifications (e.g. 257.262 Å, 1028.02 Å), and we present new ones, (e.g. the lines of the 3s²3p⁴3d–3s 3p⁵3d transition array). In addition, we highlight the presence of blends and we review which spectral lines are best for density diagnostics or for instrument calibration. The theoretical data (line intensities and level lifetimes) are benchmarked against well-calibrated spectroscopic observations of the solar corona and laboratory measurements. The agreement between theoretical and experimental data which we achieve with our new model ion is very good.