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

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 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 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_e) in the range (K) = 3.0–7.0. Values for selected transitions are given in this paper and links provided to the entire data set.