Line strength measurements for near-infrared intersystem transitions of NI

Intensities of 15 intersystem transitions and 5 LS allowed multiplets of neutral nitrogen (NI) from infrared part of the spectrum were measured by emission spectroscopy method. All allowed as well as LS-forbidden spectral lines belong to the 3p-3d transition array. The nitrogen spectra were excited in a wall-stabilized high-current arc ran in helium with small admixture of nitrogen. On the basis of these line (multiplet) intensity measurements, transition probabilities of 15 intersystem lines were determined relative to transition probabilities of appropriately chosen allowed multiplets. Finally the relative data for intersystem transitions were normalized to an absolute scale by applying reference multiplet strength values recommended by the Atomic Spectroscopy Group of NIST. The determined line strengths are compared with available calculated and — in the case of 5 transitions — also with experimental data.