Articles you may be interested inOn the possible manifestation of harmonic-anharmonic dynamical transition in glassy media in electron paramagnetic resonance of nitroxide spin probesThe structure and electronic state of photoexcited fullerene linked with a nitroxide radical based on an analysis of a two-dimensional electron paramagnetic resonance nutation spectrumMethods of preparation and the electron paramagnetic resonance spectra are given for the three prototype alkyl nitroxide free radicals: H~O, CHa(H)NO, and (CHahNO. The sigma-pi interaction theory of Karplus and Fraenkel for lac, which has been applied extensively to l4N hyperfine splitting, is examined critically by the application of linear regression to 41 uN -containing free radicals. Three different sets of uN sigma-pi interaction parameters are found which reproduce the experimental HN coupling constants to an equally high degree of accuracy. Consequently, the prediction of experimental coupling constants within the order of magnitude of solvent effects (5%-10%), should not be considered a satisfactory test of a set of theoretical 14 N interaction parameters, since the parameter values can fall within a wide range and still fulfill the test requirement. The parameter SN does not appear to play an important role in the sigma-pi interaction of these radicals.

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