Systematic measurement of the relative electron-impact excitation cross section of the 3d→2p 1P1 resonance and 3D1 intercombination lines in mid-Z neonlike ions -: art. no. 032719

The relative electron-impact cross sections for exciting the 3d-->2p P-1(1) resonance and D-3(1) intercombination lines have been measured in nine neonlike ions between Cr14+ and Kr26+. The ratio drops from about 4.4 for Cr14+ to less than unity for Kr26+ in response to an increase in relativistic effects. A measurement of the dependence of this ratio,on electron energy is presented for Fe16+. No dependence on electron energy is found. The measured ratios are generally lower than theory, showing that the relative intensity of the intercombination line is larger than predicted and illustrating the difficulty to predict electron-impact excitation cross sections in the intermediate coupling regime at the level needed for spectral diagnostics.