Spectra of Nitrogen

The emission spectrum of nitrogen has been the subject of much investigation. Both the kathode and anode spectra (Geissler tube) consist of characteristic channels. Deslandres identified three groups of lines and bands which were sharply distinguished under strong dispersion. The first group was in the visible spectrum (λ7000 - 5000), the second group partly in the visible and partly in the ultra-violet (λ5000 - 2800), and the third group wholly in the ultra-violet (λ2800 - 2000). Deslandres attributed the third group to an oxide of nitrogen, as this group disappeared if every trace of oxygen was removed by sodium. The second group was the most intense, and the bands at λ3579 and λ3372 were considered characteristic of nitrogen.

According to Trowbridge and Richards, the channelled spectrum produced by a powerful continuous discharge is changed to the bright line spectrum by the introduction of a condenser. Fowler and Strutt found that the line spectrum was characterised by a bright green line at λ5164, which is followed by green bands towards the more refrangible parts of the spectrum. These two bands are between λ4214 - λ4199 and λ1484 - λ4170.