Mass Spectrometry of Ions in Glow Discharges. III. Nitrogen and Its Mixtures with Hydrogen and Oxygen

Abstract

Ions in the negative glow and positive column of a dc glow discharge in nitrogen have been examined at a pressure of 0.4 mm and a current density of 0.03 mA/cm2. Mixtures of nitrogen with hydrogen (0.9%) and with oxygen (0.5% and 20%) were also used. In addition to N2 + and N+, the ions N3 + and N4 + are prominent in the negative glow in pure nitrogen. They appear to be formed by N++2N2→N3 ++N2, N2 ++2N2→N4 ++N2, both of which proceed to an extent dependent on field strength. With added hydrogen the ions N2H+ and NH4 + become important. N2H+ appears to be formed by at least two processes. The concentration of NH4 + is greatest in the tail of the negative glow where vibrational excitation is a possible factor and the residence time of ions is relatively long. In the presence of oxygen the ions NO2 + and N2O+ appear, as well as O2 +, but the most prominent oxygen‐containing ion is NO+. The mechanism of formation of these ions is not definitely assigned but charge‐transfer reactions may be important, as well as ion‐molecule reactions which depend to some extent upon vibrational excitation, or upon residence time in the discharge.