CHEMICAL REACTIONS IN ELECTRICAL DISCHARGES: II. THE STRUCTURE OF THE POSITIVE COLUMN IN D-C. GLOW DISCHARGES THROUGH FAST-FLOWING GASES

Abstract

After a brief summary of recent advances in the structure of the positive column of a d-c. glow discharge, general expressions are derived for rates of reaction and excitation produced by electron impact. These rate equations are expressed in terms of the easily measured electrical parameters of the discharge. Such expressions will be used in future studies of chemical reactions occurring in the positive column; a qualitative comparison to experiment is given, where possible.A general expression for the axial electric field in the positive column is obtained by equating the energy gained by the electrons in this field to that lost by collisions. The main assumption made is that axial electron concentration be constant along the column.In the second part of the paper, calculations are done which indicate that ion and electron concentration gradients exist in the positive column adjacent to the anode. It is pointed out that such a phenomenon will be pronounced only under special conditions of low transverse and high axial field, and will be enhanced with fast-flowing gases.A sample calculation is presented using the expression for the rate of electronic excitation of a species by electron impact, assuming a Maxwell–Boltzmann energy distribution for the electrons and constant elastic and inelastic collision cross sections.