Quantum-defect and distorted-wave theory applied to the resonance contribution of inelastic electron scattering

The importance of the resonance contributions to inelastic scattering of electrons from atoms and ions has been appreciated for quite some time. We have used an approximate method to compute the resonance contributions to selected inelastic transitions in O VI and S IV and compare our results with other theoretical calculations. We find that our total resonance-enhanced collision strengths are in very good agreement with other calculations. We also can accurately compute the positions of individual resonances but can sometimes be in error by a factor of 2 on individual resonance widths.