ELECTRON-IMPACT IONIZATION OF AR-2, ARKR, KR-2, KRXE, AND XE-2

Relative cross sections for electron-impact ionization of the rare-gas Van der Waals dimers Ar2, ArKr, Kr2, KrXe, and Xe2 have been measured with a mass spectrometer in the electron energy range from threshold to 180 eV. The following appearance potentials for direct ionization from the corresponding neutral dimers have been found: Ar2+: 15.2±0.2 eV, ArKr+: 14.0±0.2 eV, Kr2+: 13.45±0.3 eV, KrXe+: 12.2±0.2 eV, and Xe2+: 11.75±0.3 eV. These values agree with those obtained in recent photoelectron studies. The appearance potential of Ar2+ formation via associative ionization of argon atoms is found to be 14.6±0.2 eV. © 1979 The American Physical Society.