Interaction of Recombining Atomic Nitrogen with Gaseous Plasmas

Experiments are reviewed which measure the three-body volume recombination coefficient of neutral nitrogen atoms in nitrogen gas making use of an electron spin resonance (ESR) technique to determine the atomic concentration. The nitrogen atoms were created in an electrodeless discharge and were carried to the ESR detector by a stream of flowing gas. The temperature dependence of the atomic recombination coefficient near 300°K and the number of photons emitted in the Rayleigh afterglow bands per recombination have been determined. It has been found that the loss rate of nitrogen atoms is considerably enhanced when the atomic stream is exposed to a feeble DC discharge. The removal mechanism appears to be one of ionization of nitrogen atoms by electronic bombardment followed by a comparatively rapid ambipolar diffusion. If, however, the stream of atoms passes through a region containing a decaying afterglow plasma in nitrogen where the electronic temperature is low, it is observed that the electronic ambipolar diffusion coefficient is enhanced in the presence of atoms. The above implies an energy transfer mechanism between the recombining atoms and the cool electrons. This effect is presently being explored by observing the change in light emitted by the nitrogen electronic afterglow and the change in electronic concentration and electron-neutral collision frequency with microwaves upon intoducing atoms into the afterglow plasma.