Effect of attachment and multiple ionization on ln (α/p) against p/E curves

Abstract

Using the same assumptions as made by Swamy and Harrison in 1966, based on the Townsend theory, a plot of ln (α/p) against p/E yields a straight line. In practice, for most gases at low p/E, an up-curving occurs; this is ascribed to the presence of multiple ionization. For electronegative gases at high p/E, a faster-than-linear decrease in ln (α/p) takes place with increase in p/E; this may be shown to be due to attachment. In fact a plot of the true ionization coefficient of these gases yields a continued straight line at high p/E. The semi-empirical equation derived earlier by Swamy and Harrison for gas mixtures is extended to include multiple ionization, and reasonably good agreement for the true ionization coefficient for air is obtained from a consideration of the constituent gases.