Electron impact excitation of one- and two-electron positive ions

The distorted-wave polarised-orbital (DWPO) model is applied to the evaluation of electron impact excitation cross sections for the lowest s to s and s to p transitions in one-electron positive ions (2<or=Z<or=10) and in helium-like ions (3<or=Z<or=10 and Si12+, Ca18+ and Fe24+). The results for He+(2P) are compared with experiment, and the other results with available theoretical models, from excitation threshold to high energies.