Ionization Potentials and Probabilities for the Formation of Multiply Charged Ions in Helium, Neon and Argon

The multiply charged ions in helium, neon and argon have been studied with a mass spectrograph previously described. In helium the ${\mathrm{He}}^{+}$ ion showed up strongly but only faint evidence for the formation of ${\mathrm{He}}^{++}$ was found and no quantitative data for its relative intensity could be obtained. Neon yie ded the three ions ${\mathrm{Ne}}^{+}$,${\mathrm{Ne}}^{2+}$ and ${\mathrm{Ne}}^{3+}$ as the result of single electron impacts occurring respectively at minimum electron energies of 21.5, 63, and 125 volts. Curves which illustrate the efficiency for the formation of these ions expressed in number of ions per electron per cm per mm pressure at 0°C as a function of the electron velocity exhibit maxima for ${\mathrm{Ne}}^{+}$ and ${\mathrm{Ne}}^{2+}$ of 2.75 and 0.16 at 150 and 250 volts respectively. In argon the five ions ${\mathrm{A}}^{+}$,${\mathrm{A}}^{2+}$,${\mathrm{A}}^{2+}$, ${\mathrm{A}}^{4+}$ and ${\mathrm{A}}^{5+}$ were observed. The ionization potentials for the first four were found to be respectively, 15.7, 44, 88 and 258 volts for single impact. The efficiency curves show maxima of 11.4, 1.1 and 0.04 at 50, 115 and 250 volts for ${\mathrm{A}}^{+}$,${\mathrm{A}}^{2+}$ and ${\mathrm{A}}^{3+}$ respectively. In the curves for ${\mathrm{Ne}}^{3+}$ and ${\mathrm{A}}^{4+}$ are found several upward breaks beyond their ionization potentials which indicate other higher critical potentials for their formation.