Retarding-Potential Measurement of the Kinetic Energy of Electrons Released in Penning Ionization

Abstract

Kinetic energy of electrons released in ionization of N₂, CO, NO, COS, CO₂, C₂H₂, CH₄, C₂H₆, C₃H₈, and n‐C₄H₁₀ by means of helium atoms in metastable 2¹S and 2³S states was measured and the energy of electronically excited ionic states determined. In N₂, CO, COS, and CO₂ all accessible excited states were populated probably by a Franck—Condon transition. Ionization of NO seems to proceed through pre‐ionization of the HeNO complex in which a part of internal energy is converted into kinetic energy of He and NO⁺. In ionization of C₂H₂ and CH₄, energy which can be effectively stored in the C₂H₂⁺ and CH₄⁺ ions in the ground state was determined and the aspects of the dissociative ionization discussed. In ionization of C₂H₆, C₃H₈, and n‐C₄H₁₀, more excitation energy is conferred on the ions than in ionization by charge transfer or electron impact.