Theory and Experiments Relating to the Striated Glow Discharge in Mercury Vapor

Abstract

Theory of the glow discharge in a monatomic gas.—For the case of parallel plane electrodes with a hot cathode as source of electrons, the potential distribution and ion concentration in the Crookes dark space, negative glow, Faraday dark space and positive column are shown to be predictable from considerations of space charge and of ionization and excitation of the gas. While with weak currents there is a negative space charge throughout, sufficiently intense ionization is shown to lead to a cathode drop, followed by a region of reversed electric field in which positive ions and electrons both move toward the anode by diffusion, owing to their large concentration gradient. Still farther from the cathode the field changes to its normal direction and increases up to the positive column. In the positive column the field and concentration are uniform unless atoms excited by electron impacts in certain layers are prevented from diffusing between the layers, when striations may be obtained with periodic changes of field and of concentration. The cathode edge of each striation has a positive space charge. The theory of the arc discharge is essentially the same, the arc being simply the negative glow of the longer glow discharge.