Transition probabilities for the UV0.01 multiplet in N m

We report on large-scale ab initio multiconfiguration Hartree-Fock calculations for the UV0.01 multiplet, 2s²2p²P_J-2s2p^{2 4}P_J', in N III. The resulting transition probabilities agree very well with recent semiempirical calculations, and the lifetimes for two of the three upper levels agree with experiments. The deviation for the third level is discussed. Comparisons made with the highest quality IUE echelle spectra available - those of RR Tel and V1016 Cyg (both photoionized sources with electron densities below 10⁸ cm^-3) - show that computed branching ratios of lines sharing a common upper level are in agreement with observations to within uncertainties of ± 10%. High-quality solar limb data or stellar data from the Hubble Space Telescope could, in principle, be used to determine whether the theoretical or measured lifetimes for the discrepant level are in error. Unfortunately, stellar data for high-density plasmas (N_e > 10¹¹ cm^-3 are needed) do not yet exist, and existing solar data lack the photometric precision to address this problem.