The resonance shift in an Shyphen;band cavity was used to measure the freehyphen;electron density n in a continuous flow of rfhyphen;excited active nitrogen in the mm Hg pressure range. n varied between 107and 6times;109cmmdash;3and depended distinctly on the oxygen contamination. The ions formed presumably are NO+. By admixing known small amounts of nitric oxide to the stream it could be demonstrated that the ionization rate indeed varied linearly with the amount of NO added. At high pressures and large n the electron removal was by recombination, and at low pressures and small n it was governed by ambipolar diffusion. The value ofDp/agr; was estimated at 109mm Hg/cm. Since the NO must be practically completely dissociated by the active nitrogen, the required large ionization rate indicates that the mechanism probably involves formation of excited nitrogen molecules as an intermediate step.
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