IONIZATION AND ATTACHMENT IN O2 AND AIRLIKE N2 - O2 MIXTURES IRRADIATED BY 1.5-MEV ELECTRONS

The production and removal of thermal electrons has been studied in O2 and airlike N2: O2 mixtures between 1 and 10 Torr during continuous and intermittent irradiation by 1.5-MeV electrons. The use of a large reaction chamber and a spatially uniform electron beam flux reduces diffusion losses two orders of magnitude below those in previous experiments, and permits direct measurements of electron attachment at correspondingly lower total gas pressures. The observed rate coefficients for three-body attachment of thermal electrons at 300°K are k3(O2)=(2.12±0.14)×10-30 cm6/sec and k3(4N2: O2)=(1.10±0.07)×10-31 cm6/sec, both during irradiation and in the afterglow. The effective cross sections for ionization by 1.5-MeV electrons and all resulting secondaries are σe(O2)=(2.83±0.7)×10-18 cm2 and σe(4N2: O2)=(2.45±0.7)×10-18 cm2. These effective cross sections are larger than recently measured cross sections for primary ionization by a factor of 3.0 ± 0.8 in both gases. © 1969 The American Physical Society.