Photo-ionization of Alkyl Free Radicals

Abstract

Studies of the photo-ionization of the methyl, ethyl, propyl, and isopropyl radicals are reported. The radicals were prepared by pyrolysis of the appropriate alkyl nitrites, tetra-alkyllead compounds, and the dialkylmercury compounds. Secondary processes occurring in the energy range covered (7.2–11.7 ev) are discussed. The appearance potentials for the methyl, ethyl, propyl, and isopropyl radicals, as measured by photo-ionization—mass spectrometric techniques are 9.82±0.04, ≤8.4, ≤8.1, and ≤7.5 ev, respectively. The adiabatic transition is accessible for the methyl radical only. Hence, the ionization potential of the ethyl, propyl, and isopropyl radicals cannot be determined by ordinary photon or electron impact experiments.