EDP Sciences
Free access
Issue
A&A
Volume 493, Number 2, January II 2009
Page(s) 697 - 710
Section Atomic, molecular, and nuclear data
DOI http://dx.doi.org/10.1051/0004-6361:200809853
Published online 06 November 2008


A&A 493, 697-710 (2009)
DOI: 10.1051/0004-6361:200809853

Breit-Pauli R-matrix calculation for fine structure effective collision strengths from electron impact excitation of Mg IX

C. E. Hudson

School of Mathematics and Physics, The Queens University of Belfast, Belfast BT7 1NN, Northern Ireland, UK
    e-mail: c.hudson@qub.ac.uk

Received 26 March 2008 / Accepted 20 October 2008

Abstract
Context. Electron impact excitation collision strengths are required for analysing and interpreting stellar observations.
Aims. This calculation aims to provide fine-structure effective collision strengths for the $\ion{Mg}{ix}$ ion using a method that includes contributions from resonances.
Methods. A 26-state Breit-Pauli R-matrix calculation has been performed. The target states are represented by configuration interaction wavefunctions and consist of the 26 lowest ${\it LS}$ states, having configurations 2s2, 2s2p, 2p2, 2s3s, 2s3p, 2s3d, 2p3s, 2p3p, and 2p3d. These target states give rise to 46 fine structure levels and 1035 possible transitions. The effective collision strengths are calculated by averaging the electron collision strengths over a Maxwellian distribution of electron velocities.
Results. The non-zero effective collision strengths for transitions between the fine structure levels are given for electron temperatures ($T_{\rm e}$) in the range $\log_{10} T_{\rm e}$(K) = 3.0–7.0. Values for selected transitions are given in this paper and links provided to the entire data set.


Key words: atomic processes -- line: formation -- methods: analytical



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