Double ionization of rare gases. I. Ion formation by electron impact

Abstract
We have determined the ratio of doubly to singly charged ions for He, Ne, and Ar caused by the impact of electrons with 2 keV energy. Special attention was given to the examination of the reliability of the apparatus with respect to its handling of differently charged ions. The results do not confirm the data of Van der Wiel et al., but they are in good agreement with those of Schram et al.