Calculations of wavelengths and transition probabilities in the singlet and triplet spectra of N IV

Energies, structures, transition wavelengths and probabilities for 1s²2snl and 1s²2pnl' singlet and triplet terms of N IV are calculated and compared with available experimental data. It is suggested that the 2p4d ¹D^o and ¹F^o terms have been incorrectly identified, that 2p3p ³S lies below 2s4s ³S and that several new and unclassified lines in the beam-foil spectrum of nitrogen are due to transitions from previously unknown 2p4f terms. A tentative assignment is provided for the unclassified line at 259.434 nm.