Electron-impact excitation cross sections of the electric dipole-allowed 3s2 1S0–3s3p [Formula: see text] transition in Mg-like argon (Ar6+) are calculated using the configuration-interaction and effective many-body Hamiltonian R-matrix close-coupling methods. The near-threshold electron-impact excitation cross sections computed with the effective many-body Hamiltonian R-matrix close-coupling method are in good agreement with the benchmark experimental results.
The effects of the Breit interaction on electron impact excitation cross sections of the 1s2s3S1 metastable level of He-like ions