Electron Impact Ionization of Atomic Hydrogen and Atomic Oxygen

Abstract

The total cross sections for the ionization of atomic oxygen and atomic hydrogen have been measured by a modulated molecular beam technique. The impact energies were 100 to 500 ev for oxygen and 100 to 750 ev for hydrogen. The number of ions formed in a region defined by the intersection of an electron beam and a modulated molecular beam was compared with the number formed when the neutral beam was partially dissociated. All ions were collected, including those energetic ions formed in dissociative ionization. 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 of Tate and Smith. The results are compared with theoretical estimates and previous experimental determinations.