Effective collision strengths for the electron impact excitation of Mg\,{\sc v}

Electron impact excitation collision strengths for fine structure transitions of Mg\,{\sc v} have been determined by a Breit-Pauli $R$-matrix calculation. The target states are represented by configuration interaction wavefunctions and consist of the 19 lowest $LS$ states, having configurations 2s$^2$2p$^4$, 2s2p$^5$, 2p$^6$, 2s$^2$2p$^3$3s and 2s$^2$2p$^3$3p. These target states give rise to 37 fine structure levels and 666 possible transitions. The effective collision strengths are calculated by averaging the electron collision strengths over a Maxwellian distribution of electron velocities. Effective collision strengths for transitions between the fine structure levels are given for electron temperatures in the range $\log_{10} T_{\rm e} ({\rm K}) = 3.0 - 7.0$. Results are compared with the previous $R$-matrix calculation of Butler \& Zeippen (AASS, 1994) and the recent Distorted Wave evaluations of Bhatia, Landi \& Eissner (ADNDT, 2006).