Ambiguities of Multiradical Spectra

Often more than one kind of radical may be trapped in UV-irradiated samples at low temperature. Interpretation of the resultant complex ESR spectra requires special care to identify whether some of the ESR lines are part of a hyperfine component or whether they are due to another kind of radical. Such ambiguities may sometimes be resolved in the following ways. 

Another interesting aspect one may encounter in low-temperature solid-state photolysis is the phenomenon of pairwise trapping of two identical radicals formed by the photodecomposition of a single molecule. For example, photolysis of solid azobisisobutyronitrile at 77°K leads to pairwise trapping of two radicals separated 

The resulting ESR spectra at higher temperature become characteristic of the isolated radicals. 

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