ESR study of free radicals in irradiated single crystals of potassium hydroxylamine disulfonate

Two free radicals formed when single crystals of potassium hydroxylamine disulfonate are irradiated with gamma rays at 77°K were studied by ESR. The ESR spectra result from a predominant center (radical A) exhibiting large 14N and 1H hyperfine splittings and from lesser amounts of Fremy's radical [ȮN(SO3)22−]. The g and hyperfine tensors of these radicals have been evaluated and are discussed. Radical A, whose identity remains in doubt, may be regarded as the precursor to Fremy's radical; on warming its lines decay and those of Fremy's radical are formed. Lines from radical A decrease in strength and those of the hydroxyl radical (ȮH) grow in strength when irradiated crystals are photolyzed at 77°K. The reverse reaction occurs in the dark; the hydroxyl radical disappears and radical A is reformed.