Band Spectra in Nitrogen at Atmospheric Pressure. A Source of Band Spectra Excitation

Abstract

An apparatus, essentially an ozonizer, consisting of a cylindrical condenser, a portion of the dielectric of which is a gas, has been used as a source of band spectra excitation. Such a source can be operated with the gas at atmospheric pressure and at a temperature which is practically that of the walls. Nitrogen bands $A\to X$ have been photographed in emission at atmospheric pressure under resolution sufficient to permit measurement of part of their rotational structure. The rotational structure of four of the present bands has been computed by using the rotational constants which have been determined from other band systems in nitrogen. The agreement with the measured values is satisfactory, and makes more certain the identification of this band system. The alternation of intensity in the rotational lines is clearly visible, measurements indicating that the ratio of the intensities is 2: 1. In this source of excitation the first positive group of nitrogen is considerably weaker relative to the second positive group than in an ordinary glow discharge. The rather striking difference between this type of source and a high voltage, low current arc at atmospheric pressure is illustrated by band spectra in oxygen containing a small amount of nitrogen. In the latter source the principal emission is the Runge bands of oxygen while in the former the only prominent material is the second positive group of nitrogen.