Multiple Ionization in Argon and Krypton by Electron Impact

Abstract

The formation of multiply charged ions by electron impact in argon and krypton is studied with a mass spectrometer. The behavior of the ionization cross section as a function of electron energy is investigated for electron energies up to 600 ev. The ionization potentials in ev are determined to be as follows: ${\mathrm{Kr}}^{\text{2+}}\text{\hspace{0.17em}38.45±0.1,}{\mathrm{Kr}}^{\text{3+}}\text{\hspace{0.17em}75.6±0.5,}{\mathrm{Kr}}^{\text{4+}}\text{\hspace{0.17em}146.6±2,}{\mathrm{Kr}}^{\text{5+}}\text{\hspace{0.17em}217.5±10,}{\mathrm{Kr}}^{\text{6+}}\text{\hspace{0.17em}350±10,}{\mathrm{Ar}}^{\text{2+}}\text{\hspace{0.17em}43.4±0.3,}{\mathrm{Ar}}^{\text{3+}}\text{\hspace{0.17em}84.8±0.5,}{\mathrm{Ar}}^{\text{4+}}\text{\hspace{0.17em}150.0±5}$ . The shapes of the ionization curves near threshold are studied and discussed in terms of the threshold law for ionization. The maximum cross sections for each multiply charged ion is determined relative to that of the singly charged ion and compared to data obtained by previous investigators.