Probability Curves near Threshold for the Formation of He+, Ne++, A++, Kr++, and Xe++ by Electron Impact

Abstract

The formation of ${\mathrm{He}}^{+}$, ${\mathrm{Ne}}^{++}$, ${\mathrm{A}}^{++}$, ${\mathrm{Kr}}^{++}$, and ${\mathrm{Xe}}^{++}$ as a function of electron energy is studied with essentially monoenergetic electrons. The ${\mathrm{He}}^{+}$ curve obtained in this way for an energy range of eight volts above the ionization threshold does not exhibit any detectable departure from linearity. The accuracy is such that the difference between a 1.0 and 1.1 power curve is detectable for this energy range. The ionization probability curves of the doubly charged ions is interpreted as the superposition of linear excitation curves arising from each of the ${}_{}{}^3{}_{}{}^{}P_2^{}{}_{}{}^{}$, ${}_{}{}^3{}_{}{}^{}P_1^{}{}_{}{}^{}$, ${}_{}{}^3{}_{}{}^{}P_0^{}{}_{}{}^{}$, ${}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}$, and ${}_{}{}^1{}_{}{}^{}S_0^{}{}_{}{}^{}$ states of the ions.