Paramagnetic Resonance of Alkyl Radicals from Dissociative Electron Attachment in γ-Irradiated Organic Glass

The radicals CH3·, CH3CH2·, CH3CH2CH2·, (CH3)3C·, (CH3)3CCH2·, and C6H5ĊHCH3 have been identified by EPR in γ-irradiated dilute solutions of the corresponding halides in 3-methylpentane at 77°K. For 0.4 mole % CH3I, G(CH3·)=1.2. Methyl radicals disappear by some first-order rate process for which k=4.6×10−4 sec−1. Other radicals did not decay measurably under similar conditions. The results are consistent with the mechanism of dissociative thermal electron attachment, RX+e−→R·+X−, which is an efficient, selective process whenever the electron affinity of X exceeds the bond dissociation energy of R—X.