Large-scale multiconfiguration Dirac-Hartree-Fock calculations for astrophysics: C-like ions from O iii to Mg vii

Large-scale multiconfiguration Dirac–Hartree–Fock calculations are provided for the n ≤ 5 states in C-like ions from O iii to Mg vii. Electron correlation effects are accounted for by using large configuration state function expansions, built from sets of orbitals with principal quantum numbers n ≤ 10. An accurate and complete data set of excitation energies, wavelengths, radiative transition parameters, and lifetimes is offered for the 156 (196, 215, 272, 318) lowest states of the 2s22p2, 2s2p3, 2p4, 2s22p3s, 2s22p3p, 2s22p3d, 2s2p23s, 2s2p23p, 2s2p23d, 2p33s, 2p33p, 2p33d, 2s22p4s, 2s22p4p, 2s22p4d, 2s22p4f, 2s2p24s, 2s2p24p, 2s2p24d, 2s2p24f, 2s22p5s, 2s22p5p, 2s22p5d, 2s22p5f, and 2s22p5g configurations in O iii (F iv, Ne v, Na vi, Mg vii). By comparing available experimental wavelengths with the MCDHF results, the previous line identifications for the n = 5, 4, 3 → n = 2 transitions of Na vi in the X-ray and EUV wavelength range are revised. For several previous identifications discrepancies are found, and tentative new (or revised) identifications are proposed. A consistent atomic data set including both energy and transition data with spectroscopic accuracy is provided for the lowest hundreds of states for C-like ions from O iii to Mg vii.