MEASUREMENT OF DRIFT VELOCITY AND LONGITUDINAL DIFFUSION-COEFFICIENT OF ELECTRONS IN PURE OXYGEN AND IN OXYGEN-ARGON MIXTURES

The electron transport coefficients, the drift velocity W, the product of the gas number density and the longitudinal diffusion coefficient NDL and the ratio of the longitudinal diffusion coefficient to the ele ctron mobility D-L/mu of electrons were measured in pure oxygen over t he E/N range 1.7-350 Td and in two oxygen-argon mixtures (with 1.01% a nd 4.994% oxygen) from about 0.03 to 3 Td by using a double-shutter el ectron drift tube with a variable drift distance. The present NDL and D-L/mu were the first measured over almost the entire part of the pres ent E/N range. The drift velocities in the mixtures exhibited a typica l negative differential conductivity and they will be important in tes ting existing vibrational excitation cross sections for the oxygen mol ecule.