Nitrogen Afterglow

Abstract

IN a recent communication in Nature, L. Herman and R. Herman¹ have given an account of their spectroscopic study of the complex afterglow in nitrogen immediately after the discharge is stopped. These short-lived afterglows have also been extensively studied by Kaplan². In this connexion, Herman and Herman remark that it seems difficult to explain the characteristics of the complex afterglow as recorded by them with the help of the theory of active nitrogen proposed by me³. It appears, however, that these authors have missed the very important point that my theory Was developed for the long-lived Lewis — Rayleigh afterglow, and not for the short-lived Kaplan afterglow, which is quite a distinct phenomenon. According to my hypothesis, the Lewis — Rayleigh afterglow phenomena, for example, the long life, the rate of decay, ionization, the characteristic spectrum (selected bands from the first positive group), etc., can be very satisfactorily explained if it is assumed that the active substance in the glow is N₂+(X') ions. The Kaplan afterglows, however, contain besides N₂+(X') ions other particles such as N₂+(A'), N, N^' which are responsible for the complex nature of the short-lived spectrum. It may, however, be mentioned in this connexion that in some of his experiments Kaplan has observed the persistence of the first negative bands for several seconds after the discharge is stopped. This provides a direct proof of the presence of N₂+ ions, at least in the first stage of the afterglow. According to my hypothesis, the N₂+ ions continue their existence even after the short-lived afterglows have died out and produce the phenomena associated with the Lewis — Rayleigh afterglow.