ABSENCE OF HYDROGEN ATOM PRODUCTION IN RADIOLYSIS OF SOLID HYDROCARBONS

Radiolysis of ethane, n-hexane, 3-methylpentane, 3-methylpentane-d14, or methylcyclohexane at 4°K produces the expected esr spectra of trapped free radicals, but no evidence of trapped hydrogen atoms, although the H atom doublet is present with the CH3 radical spectrum when CH4 is irradiated. Radiolysis of 3-methylpentane-du at temperatures in the range from 20 to 50°K produces no trapped D atoms, although it has been shown that D atoms from the photolysis of DI in this matrix can be trapped in this temperature range. The presence of 0.3 mol % isobutene in CH4 during irradiation at 4° K does not reduce the trapped H signal. Irradiation of 1 mol % C2H6 in Ar at 4°K produces little or no H atom yield compared to that from 1 mol % CH4 in Ar. These observations lead to the conclusion that the free radicals formed by radiolysis of solid hydrocarbons are not produced by elimination of H atoms. Ion-molecule reactions are, therefore, the probable mode of formation.