Ionization Afterglow Measurements on Nitrogen

The ionization afterglow experiments which are described utilize a beam of high-energy electrons (20 to 30 Mev) to produce a uniform and known concentration of ionization in a gas sample. Measurements of the electron density and collision frequency are then performed by observing the interaction of the free electrons with a probing microwave field. Studies of nitrogen have indicated that the apparent rate of electron thermalization at slightly epithermal energies is consistent with elastic scattering alone. The collision frequency at thermal energies is in good agreement with that determined from drift experiments. Electron-ion recombination is anomalous because the apparent recombination coefficient is afunction of the initial ionization intensity. This observation may be ascribed to the influence of metastables.