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

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

Received: 17 March 2008
Accepted: 13 November 2008

Abstract

Context. Electron-impact excitation collision strengths are required for the analysis and interpretation of stellar observations.

Aims. This calculation aims to provide effective collision strengths for the Mg V ion for a larger number of transitions and for a greater temperature range than previously available, using collision strength data that include contributions from resonances.

Methods. A 19-state Breit-Pauli R-matrix calculation was performed. The target states are represented by configuration interaction wavefunctions and consist of the 19 lowest LS states, having configurations 2s²2p⁴, 2s2p⁵, 2p⁶, 2s²2p³3s, and 2s²2p³3p. These target states give rise to 37 fine-structure levels and 666 possible transitions. The effective collision strengths were 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  in the range = 3.0 - 7.0. Data for transitions among the 5 fine-structure levels arising from the 2s²2p⁴ ground state configurations, seen in the UV range, are discussed in the paper, along with transitions in the EUV range – transitions from the ground state ³P levels to 2s2p^5 3P^o levels. The 2s²2p^4 1D–2s2p^5 1P^o transition is also noted. Data for the remaining transitions are available at the CDS.