Volume 499, Number 3, June I 2009
|Page(s)||943 - 954|
|Section||Atomic, molecular, and nuclear data|
|Published online||16 April 2009|
R-matrix electron-impact excitation data for B-like Si and its application in cool stars
Department of Physics, University of Strathclyde, Glasgow, G4 0NG, UK e-mail: firstname.lastname@example.org
Accepted: 2 April 2009
We present the results of an intermediate coupling frame-transformation R-matrix calculation for the electron-impact excitation of Si9+. The target and close-coupling expansions are both taken to be the 125 fine-structure levels (58 LS terms) belonging to the configurations 2sx2py () and 2s2p3l (α+β = 2, l = s, p, and d). Due to the additional resonances included in our calculation, we find significant differences at low temperatures with the widely used n = 2 2 excitation rates, also obtained with the R-matrix method, as well as with the n = 2 3 excitation rates calculated by using the distorted wave (DW) approximation. We present a list of prominent transition lines and comparisons with SERTS and Hinode/EIS EUV spectra of the solar corona, SUMER observations for the quiet sun, as well as Chandra LETG and Rocket soft X-ray spectra of the Procyon corona and solar flares, respectively. Line emissivities of some transitions are enhanced up to 40% when compared with those obtained from using the previous atomic data at the same electron density (1.6 109 cm-3) and temperature (1.3 106 K). The comparison with Chandra LETG observation of Procyon reveals that the 3s-2p line flux was significantly underestimated (by a factor of 4-5) in previous analyses. Some EUV and soft X-ray emission line ratios are -sensitive and -insensitive. Estimated electron densities from them shift downwards due to the new resonant-enhanced excitation data used in the present modelling.
Key words: atomic data / atomic processes / plasmas / stars: coronae / X-rays: stars / ultraviolet: solar system
© ESO, 2009
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