Absorption by Atomic Nitrogen in the Extreme Ultraviolet

In the investigation of the absorption spectrum of helium-nitrogen discharges, a new Rydberg series was observed in the region 694-612 A. The series was also found in the absorption spectrum of active nitrogen. In the experiments, the Hopfield continuum of helium was used as background. Twelve members of the series were observed and yielded a convergence limit of 164012 + 15 which coincided within experimental error with the 5S state of N ii at 163999 . The spectrum is attributed to transitions from the `S ground state of the nitrogen atom to the Rydberg terms 2s 2p3(5S ) np `P. As a result of auto-ionization, all the lines are broadened and show an asymmetric structure.