Ultraviolet Spectra of the Nitrogen Pink Afterglow

Ultraviolet spectra from 4200 to 1150 Å of the recurrent, brilliant afterglow in fast-flowing pure nitrogen are obtained using a vacuum spectrometer at 0.5-Å resolution with photographic and photoelectric detection. Molecular emission features generally resemble those of a direct discharge. Atomic lines from the 10.7-eV 3s 2P level are present, but there are none from the 10.4-eV 3s 4P level. Electrical quenching by a 60-kc/sec field reduces the N2+ bands more sharply than the N2 bands or the N lines. Optical absorption and other measurements show that the concentrations of ground-state and low-lying metastable atoms are little affected by this afterglow or by its quenching.