Theoretical values for the [O iii] 5007/4959 line-intensity ratio and homologous cases

The magnetic-dipole probabilities for the 1 D 2 3 P 2 and 1 D 2 3 P 1 transitions in carbon-like and oxygen-like ions are calculated up to atomic number Z 12, including relativistic corrections to the magnetic dipole operator. The ratio of the probabilities for these two transitions is found to change by up to 5 per cent compared with previous theoretical work, none of which included these relativistic corrections, with the effect being largest for the near neutral ions. The transition probability ratio for the [O iii] 5007 and 4959 A lines is found to be 3.01, implying an intensity ratio of 2.98, in significantly better agreement with the observed ratio than the earlier theoretical work.