PRODUCTION OF OXYGEN ATOMS IN A MICROWAVE DISCHARGE AND RECOMBINATION KINETICS IN A GAS FLOW SYSTEM

Oxygen atoms have been produced by a 2·45 GHz discharge in an oxygen molecular gas flow, and e.p.r. techniques used to observe the decay of atoms in the flow tube. The decay is first order in atom concentration and proceeds in the gas phase by an ozone process with a rate constant of (4·5± 0·2) × 107 l2 mol-2 s -1, with a small contribution from the quartz surface of the flow tube. From the extrapolation of an atom decay curve and by using the oxygen molecule as an e.p.r. calibration standard, absolute atom concentrations in the discharge have been obtained. In the pressure range 1-10 torr (133-1330 N m -2) and with a discharge power of 15 W, the molecular dissociation varies from 0·02% to 0·9% atom-mole fraction with a maximum of 2% at 6 torr, and the percentage of the power dissipated in the gas used for dissociation varies from 0·05% to 5%. The yield obtained from a 15 W discharge with a flow velocity of 2·5 m s-1 was approximately 4 g kwh-1.