[O ii] line ratios

Based on new calculations, we reconfirm the low- and high-density limits on the forbidden fine-structure line intensity ratio [O ii]I(3729)/I(3726): and . Employing [O ii] collision strengths calculated using the Breit–Pauli R-matrix method, we rule out any significant deviation due to relativistic effects from these canonical values. The present results are in substantial agreement with older calculations by Pradhan, and validate the extensive observational analyses of gaseous nebulae by Copetti & Writzel and Wang et al. that reach the same conclusions. The present theoretical results and the recent observational analyses differ significantly from the calculations by McLaughlin & Bell and Keenan et al. The new Maxwellian averaged effective collision strengths are presented for the 10 transitions among the first five levels to enable computations of [O ii] line ratios.