Reaction rate constants in steady-state hollow cathode discharges: N2 + H2O reactions

Abstract

In a cylindrical hollow cathode discharge in N₂ with traces of H₂O, there is a distribution of ion types from the edge of the negative glow to the axis of the cylinder. This distribution was explored by using a small, radially movable probe with an entrance aperture to a mass spectrometer in the probe. Ions could then be extracted from the negative glow plasma from any desired radial location in the cylinder. The results show ${\mathrm{N}}_2^{+}$ and N⁺ at the edge of the glow giving way to N₂H⁺, H₂O⁺, and H₃O⁺ toward the axis. Clearly, ion‐molecule reactions are proceeding in the field‐free negative glow region. Quantitative rate constant measurements were obtained for formation and destruction of N₂H⁺, ${\mathrm{H}}_2^{+}$ , N⁺, and the formation of H₂O⁺ and H₃O⁺. The measurements on ${\mathrm{N}}_2^{+}$ and N⁺ formation by electron collisions give values for the density of high energy electrons in the negative glow. Adequate agreement is found with values obtained by other workers using other methods, where overlap occurs. The present new and different method thus lends support to older findings as well as providing new information.