On the electric breakdown of electronegative gases

Two years ago at this Conference we presented a paper in which it was demonstrated that the sparking potentials of simple hydrocarbon gases could be related directly to certain physical properties of the molecules of which the gases were composed(1). In order to accomplish this it was first necessary to derive an expression relating the first Townsend coefficient, α, of a gas to the pressure, P, the applied electric field, E, and to the elastic and inelastic cross-sections of the individual gas molecule. By introducing certain realistic assumptions regarding the energy dependence of these cross-sections, it was possible to show that, (2) equation where Q represents the total elastic cross-section of the gas molecule, and ε_i its ionization threshold.