Electron Impact Study of Nitric Oxide Using a Modified Retarding Potential Difference Method

Abstract

An electron impact study of NO was made using the retarding potential difference method for producing the effect of a monoenergetic electron beam. In this modification of the method the electron retarding potential is provided by the potential minimum which exists between the anode and cathode of a space‐charge limited diode. The ionization potential of NO was found to be 9.25±0.02 ev and the ionization efficiency curve for NO⁺ to be nonlinear near the onset. This curvature can be attributed to the difference in the equilibrium internuclear distances of NO and NO⁺. Appearance potentials were obtained for the formation of N⁺, O⁺, and O^‐ ions from a number of processes. With the exception of O^‐ ions formed by electron capture, it was not necessary to postulate that any of the ions are formed with excess kinetic energy. The appearance potentials of all the processes are consistent, within experimental error, with a value of 6.50 ev for the dissociation energy of NO. The shape of the resonance capture curve for O^‐ formation was used to construct part of the potential energy diagram for the NO^‐ ion.