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

The magnetic-dipole probabilities for the D-1(2)-P-3(2) and D-1(2)-P-3(1) t ransitions in carbon-like and oxygen-like ions are calculated up to atomic number Z = 12, including relativistic corrections to the magnetic dipole op erator. The ratio of the probabilities for these two transitions is found t o change by up to 5 per cent compared with previous theoretical work, none of which included these relativistic corrections, with the effect being lar gest for the near neutral ions. The transition probability ratio for the [O III] 5007 and 4959 Angstrom lines is found to be 3.01, implying an intensi ty ratio of 2.98, in significantly better agreement with the observed ratio than the earlier theoretical work.