On the Optimum Use of Ionization-Efficiency Data

Abstract

The electron energy spread causes much fine detail in ionization efficiency curves to be obscured. The reduction of this spread by electron velocity analyzers is experimentally quite difficult. The present paper examines whether it is possible to reduce the effect of the energy spread by any analytical method. It is found that the problem is very similar to that of the detection of radar signals in noise, and that similar methods can be applied. It is shown that typical ionization efficiency data contain a very much greater amount of information than is generally believed. Methods are developed for obtaining a marked reduction in the scatter in the experimental data and for reducing the effective electron energy spread by a factor of four or five times. The methods do not require an exact knowledge of the form of the electron energy spread, although the better this knowledge, the better the ultimate result. Tests made on several artificial examples and on two actual cases show that the methods are of some promise. The results of this study also indicate a possible unconventional solution to the problem of achieving even higher resolution in energy in experimental ionization efficiency curves.