Electron Impact Ionization of Atomic Nitrogen

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Abstract
The total cross sections for the ionization of atomic nitrogen by electron impact have been measured between 25 and 750 eV using a modulated molecular beam technique. The neutral beam source was a pulsed dc discharge which dissociated about 20% of the molecules. The number of ions formed in a region defined by the intersection of an electron beam and the modulated molecular beam was compared with the number of ions formed when the neutral beam was partially dissociated. All ions were collected, including those energetic ones formed in the dissociative ionization of molecular nitrogen. The degree of dissociation was measured with a mass spectrometer. From the data, the ratios of the atomic to the molecular ionization cross sections were obtained. The absolute atomic values were calculated by multiplying these ratios by the molecular ionization cross sections measured by Tate and Smith. The atomic cross sections are lower than those calculated by Seaton.