Active Nitrogen and the Auroral Spectrum

Abstract

IN my letter in a recent number of NATURE^I described an afterglow in nitrogen in which the first negative bands of N₂ were present, and in which the excitation of the first positive bands was different from that hitherto observed in nitrogen afterglows. At the time the letter was written, no photograph of the afterglow intense enough to print had been obtained. Fig. 1 shows a photograph of the spectrum of the afterglow which has been obtained since then, and it is to be noted that with the exception of the green auroral line, the afterglow spectrum is remarkably like the auroral spectrum. In my first letter it was stated that the second positive bands were completely missing from the afterglow, and that was true of the plate which was described in that letter, but a trace of the second positive group can be very easily seen on the present plate and they have been obtained with considerable intensity on a plate taken on a small quartz Hilger spectrograph. The arrows on Fig. 1 point to first positive band sequences which originate on V = 16, 17, 18, etc., and it is seen that these sequences are present on the afterglow plates also.