A series of experiments on the ionization of noble gases by noble gas atoms is described. The results obtained are the following:
1. Preliminary results by Beeck showing little velocity dependence for ionization of argon by argon atoms between 50 and 120 volts, and showing an ionization of neon by argon atoms in this energy range are found to be due to secondary effects, principally due to argon radiation.
2. Positive evidence for the ionization of one noble gas by atoms of another is given for argon atoms bombarding neon, krypton, and xenon.
3. The inset potentials for ionization of the above combinations are measured, and are believed to be comparable in accuracy to those measured by other methods, since the measured value for argon in argon (48 volts) agrees with that of the best previous work. The values found are: argon in neon, approximately 130 volts; argon in krypton, 50 volts; argon in xenon, 55 volts.
