The short-duration afterglow or pink afterglow of nitrogen is superimposed on the well-known long-duration, Lewis—Rayleigh afterglow as a bright flash of milliseconds duration, separated from the discharge by a short delay. The spectrum shows the same band systems as does the discharge, with different relative intensities. The flash of light coincides with flashes of heat and ionization. A comprehensive mechanism, including the various modifications of the short-duration afterglow, is presented. During the delay time, metastable molecules, generated by the ever-present Lewis—Rayleigh afterglow, accumulate until their concentration is sufficient for collisions between two metastables to occur. These, supported by high vibration, generate ions N2+. Their excitation is due to fast electrons or highly vibrating molecules. The periodic occurrence of the pink afterglow is attributed to temperature effects. The blue and green afterglows are explained by modifications of the same idea.
O. OLDENBERG, "Mechanism of the Short-Duration Nitrogen Afterglow," J. Opt. Soc. Am. 61, 1092-1098 (1971)