Abstract
Measurements have been completed of electron‐density relaxation in cesium‐seeded plasmas perturbed from thermal equilibrium at temperatures in the 1500° to 2000°K range. The gases consisted of 0.1 to 20 Torr Cs vapor in atmospheric pressure argon or helium. Electron densities ranged over 1.9×1011 to 3.8×1013 cm−3 and relaxation times over 30×10−6 to 50×10−3 sec. The results indicate that charge production and loss are dominated by the atomic‐ion process Cs+e+3.89 eV↔Cs++2e at the higher temperatures, and by the molecular‐ion process Cs+Cs+2.82 eV↔Cs2++e at the lower temperatures and higher cesium pressures. At the lower temperatures and lower cesium pressures the dominant process is ambipolar diffusion. The results obtained when the atomic‐ion process dominates agree well with calculations based on the equilibrium properties of the gas and recent theory for two‐electron, three‐body recombination. The rate of the molecular‐ion process corresponds to a two‐body recombination coefficient of approximately 1×10−8 cm3/sec at temperatures of 1250° to 1400°C, a value small relative to that derived from earlier experiments. All evidence indicates that, despite their numerical preponderance, the argon and helium atoms play no significant roles beyond those of thermal bath and diffusion barrier.