Abstract
Four organic solids, adamantane, guanosine, 2'-deoxyuridine, and 5-iodo-2'-deoxyuridine were ..gamma.. irradiated in the dose range from 0 to 200 Mrad and their positron annihilation lifetimes and ESR signals measured, with and without subsequent thermal annealing. No consistent correlation between the positron lifetime data, lambda/sub 1/, lambda/sub 2/, and I/sub 2/ and free-radical concentration or absorbed radiation dose could be observed. On the basis of these results, it appears that the positron annihilation method is not a direct technique for the study of paramagnetic centers or radicals in irradiated solid organic materials because the interactions of positron or positronium with these species are frequently obscured by the response of the positron annihilation process to radiation-induced structural changes in these solid materials.
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