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 N2+ 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+, H2+, N+, and the formation of H2O+ and H3O+. The measurements on N2+ 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.