Volume 570, October 2014
|Number of page(s)||9|
|Section||Atomic, molecular, and nuclear data|
|Published online||16 October 2014|
Atomic data for astrophysics: improved collision strengths for Fe viii⋆
DAMTP, Centre for Mathematical Sciences,
Wilberforce road Cambridge,
2 Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK
Received: 1 July 2014
Accepted: 12 August 2014
We describe, and present the results of, a new large-scale R-matrix scattering calculation for the electron collisional excitation of Fe viii. We first discuss the limitations of the previous calculations, in particular concerning some strong EUV lines observed in the solar corona by the Hinode EUV Imaging Spectrometer. We then present a new target which represents an improvement over the previous ones for this particularly complex ion. We developed a new method, based on the use of term energy corrections within the intermediate coupling frame transformation method, to calculate the collision strengths. We compare predicted and observed line intensities using laboratory and solar spectra, finding excellent agreement for all the main soft X-ray and extreme ultraviolet (EUV) transitions, using the present atomic data. In particular, we show that Fe viii EUV lines observed by Hinode EIS can now be used to provide reliable electron temperatures for the solar corona.
Key words: atomic data / line: identification / techniques: spectroscopic
The full dataset (energies, transition probabilities and rates) is only 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 (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/570/A56
© ESO, 2014
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