The ionization potentials of methyl, allyl, and benzyl radicals have been measured directly by electron impact. The values found were methyl 9.95±0.03 ev, allyl 8,16±0.03 ev, and benzyl 7.73±0.08 ev. The radicals were produced by thermal decomposition of suitable compounds in a mass spectrometer designed for the study of free radicals. Reactions of the radicals after formation led to the expected dimers, but the disproportionation reactions were found to be negligibly slow.
The Journal of Chemical Physics22, no. 4: 621–625.