Electron-impact excitation of Mg IV using the R-matrix method

The R-matrix method is used to calculate electron impact collision strengths for transitions in Mg IV from its ground state ( 2 P o ) to the eleven lowest excited states. Configuration interaction wavefunctions are used to represent the twelve target states which are included in the calculation. The effect of resonances converging onto these excited states is included in the calculations. Finally, collision rates have been calculated from the ground state to the excited states by assuming a Maxwellian electron distribution for the incident electrons. These are tabulated over a wide temperature range. This is the first detailed calculation for this ion in which the effects of exchange, channel couplings and short-range correlations are properly taken into account.