An electron impact study of NO was made using the retarding potential difference method for producing the effect of a monoenergetic electron beam. In this modification of the method the electron retarding potential is provided by the potential minimum which exists between the anode and cathode of a space-charge limited diode.
The ionization potential of NO was found to be 9.25±0.02 ev and the ionization efficiency curve for NO+ to be nonlinear near the onset. This curvature can be attributed to the difference in the equilibrium internuclear distances of NO and NO+. Appearance potentials were obtained for the formation of N+, O+, and O- ions from a number of processes. With the exception of O- ions formed by electron capture, it was not necessary to postulate that any of the ions are formed with excess kinetic energy. The appearance potentials of all the processes are consistent, within experimental error, with a value of 6.50 ev for the dissociation energy of NO. The shape of the resonance capture curve for O- formation was used to construct part of the potential energy diagram for the NO- ion.
Using a generalized formulation of Kirchhoff's law it is possible to relate the equilibrium electromagnetic radiation spectrum of a body to its absorptivity spectrum. The microwave absorptivity of a uniform anisotropic plasma slab to a normally incident electromagnetic wave is obtained by matching fields at the boundaries and is solved completely for the model chosen.The absorptivity spectrum of the plasma slab is computed for waves propagating parallel to and normal to an applied static magnetic field for various electron densities, electron collision frequencies, and slab thicknesses. Peaks in the absorptivity spectrum occur around the edges of the "stop-bands". In general, the absorptivity increases with slab thickness and collision frequency. The effect of internal reflections is included and gives rise to undulations in the absorptivity spectrum.
An experimental study of the properties of supersonic plasma streams which have been seeded with small amounts of an electronegative gas is described. It has been found that striking reductions of the electron and ion densities of the plasma can be achieved using sulfur hexafluoride (SF6) as the seed gas. The properties of seeded argon streams at pressures of 1 Torr and velocities of about Mach 2 have been studied using double-probe and microwave (9.2 Gc/sec) scattering techniques. The results show that when the SF6 is introduced with a concentration of only 5 × 10−4 relative to that of the argon in the stream, the plasma is quenched almost completely. Under these conditions the reflection of microwaves from the stream is reduced by 20 dB and the probe measurements show the presence of the ``hole'' cut in the plasma by the SF6. Measurements of seeding with argon, nitrogen, and oxygen in the argon streams are also discussed.
When temperature fluctuations are large in a plasma, the floating potential cannot be used to calculate electric fields. This note describes a method which allows the calculation of the plasma potential as a function of time from measured values of the electron temperature and the floating potential. An application of this technique to the evaluation of electric fields in a reflex discharge is briefly outlined.
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