Analyses of the electron-spin-resonance (ESR) hyperfine powder spectra of nitroxide radicals enriched with 15N (I=1/2)

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Abstract
A detailed investigation has been performed to analyze the electron‐spin‐resonance (ESR) properties of a nitroxide radical (TANOL) isotopically enriched with 15N with a nuclear spin I=1/2 in amorphous samples of a polycarbonate polymer. Unlike the case of 14N with I=1, the 15N ESR hyperfine powder spectra consist of two components that are well resolved at an X‐band microwave frequency and each hyperfine component displays resolved powder‐pattern structures so that the values of all the principal Zeeman and hyperfine coupling constants can be unambiguously determined as gx= 2.0096, gy= 2.0062, gz =2.0022, Ax/(gx μB)=−1.00 mT, Ay/(gy μB) =−1.00 mT, Az/(gz μB) =−4.89 mT, with an accuracy of ±0.0004 for the gi values and ±0.0015 mT for the Ai/(gi μB) values.