Active Nitrogen at High Pressure

Abstract

A pure nitrogen afterglow has been studied spectroscopically at pressures up to 1 atm and up to several seconds after the discharge. The first positive bands of nitrogen continue to show an unchanged preferential enhancement of bands with v′=11 at high pressure, but their decay with time, measured photoelectrically, indicates that at high pressure N(4S) atoms must be removed by a more rapid process than recombination in triple collisions; it is suggested that this may be a two-body reaction with an oxide of nitrogen. Forbidden radiation from O, N, and N2 predominates over the first positive bands at high pressure, and a high degree of immunity toward deactivating collisions is shown to be required for the metastable states N(2P), O(1S), and N2(A 3Σu+). The absolute intensity and decay of the forbidden radiation indicates that O(1S) must be created in the afterglow while N(2P), and to some extent N2(A 3Σu+), survive from the discharge. The observations favor a long radiative lifetime near 1 sec for N2(A 3Σu+).