Mass Spectrometry of Ions in Glow Discharges. II. Negative Glow in Rare Gases

Abstract

The ions in the negative glow were examined at pressures of about 0.4 mm and currents of about 0.2 ma. Most of the work was done with argon but some measurements were made with helium and with helium‐argon and argon‐krypton mixtures. To clarify the role of impurities, some work was done with the addition of 1.25% hydrogen to the argon. The results confirm that the ions of the principal gas or gases are produced by the impact of ``primary'' electrons. Evidence is obtained that when small amounts of gases having sufficiently low ionization potentials are present, they are ionized by interaction with the metastable atoms of the principal gas. Ar₂⁺ appears to form in the negative glow mainly by $${\mathrm{Ar}}^{+}\text{+2}\mathrm{Ar}\to {\mathrm{Ar}}_2^{+}+\mathrm{Ar},$$ but it is confirmed that in the positive column a process depending mainly on excitation must be dominant. The formation of ArH⁺ from impurities is thought to occur principally by the reaction of metastable argon atoms with hydrogen atoms, the latter being produced from various sources by electron impact. In the presence of appreciable quantities of hydrogen, the reaction $${\mathrm{Ar}}^{+}+{\mathrm{H}}_2\to {\mathrm{ArH}}^{+}+\mathrm{H}$$ appears to contribute but is only important at the cathode edge of the negative glow. The extremely persistent formation of H₃O⁺ from traces of water suggests that long‐lived excited states of water may exist, and be responsible for this effect.