Low-Energy Electron Scattering from Atomic Oxygen

The total cross section for the scattering of electrons by atomic oxygen has been measured as a function of electron energy from 2.3 to 11.6 ev. The number of electrons scattered from a region defined by the intersection of an electron beam and a modulated molecular oxygen beam was compared with the number scattered when the oxygen beam was partially dissociated. A radio-frequency discharge dissociated about 30% of the molecules. The degree of dissociation was measured with a mass spectrometer. From the data, the ratios of atomic to molecular scattering cross sections were obtained. The absolute atomic values were calculated by multiplying these ratios by the molecular oxygen cross sections obtained by Brüche. The result is a virtually constant cross section of $(6.2\mathrm{}\pm 0.5)\pi {a_0}^2$ in the entire energy range studied. This result is compared with five theoretical estimates.