Atomic data for astrophysics: Fe xi soft X-ray lines^⋆

¹ DAMTP, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, CB3 0WA, UK
e-mail: g.del-zanna@damtp.cam.ac.uk
² Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK

Received: 18 June 2012
Accepted: 16 November 2012

Abstract

We present new large-scale R-matrix (up to n = 4) and distorted wave (up to n = 6) scattering calculations for electron collisional excitation of Fe xi. These data are needed for the analysis of soft X-ray spectra of astrophysical plasmas, where strong n = 4 → n = 3 transitions are present. As found in previous work on Fe x, Fe xii, and Fe xiii, resonances from within the n = 4 levels and cascading from higher levels significantly increase the intensities of these lines. We provide a list of the strongest lines, many of which are unidentified. The present larger model produces intensities for decays from n = 3 levels mostly consistent with our previous work, however significant enhancements for some lower levels are found, in particular for the 3s² 3p³ 3d ⁵D which can be used to measure electron temperatures in the solar corona with the Hinode/EIS spectrometer.