Volume 543, July 2012
|Number of page(s)||10|
|Section||Atomic, molecular, and nuclear data|
|Published online||12 July 2012|
Atomic data for astrophysics: Fe xii soft X-ray lines⋆
1 DAMTP, Centre for Mathematical Sciences, Wilberforce Road, Cambridge, CB3 0WA, UK
2 Department of Physics and Astronomy, University College London, Gower Street, London, WC1E 6BT, UK
3 Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK
Received: 12 February 2012
Accepted: 30 May 2012
We present new large-scale R-matrix (up to n = 4) and distorted-wave (DW, up to n = 6) scattering calculations for electron collisional excitation of Fe xii. The first aim is to provide accurate atomic data for the soft X-rays, where strong decays from the n = 4 levels are present. As found in previous work on Fe x, resonances attached to n = 4 levels increase the cross-sections for excitations from the ground state to some n = 4 levels, when compared to DW calculations. Cascading from higher levels is also important. We provide a number of models and line intensities, and list a number of strong unidentified lines. The second aim is to assess the effects of the large R-matrix calculation on the n = 3 transitions. Compared to our previous (n = 3) R-matrix calculation, we find overall excellent agreement to within a few percent, however a few key density diagnostic EUV intensities differ by about 60% at coronal densities. The new atomic data result in lower electron densities, resolving previous discrepancies with solar observations.
Key words: atomic data / line: identification / techniques: spectroscopic / Sun: corona
The full dataset (energies, transition probabilities and rates) are available in electronic form at our APAP website (http://www.apap-network.org) as well as at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/543/A139
© ESO, 2012
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