Anisotropic Hyperfine Structure in ESR Spectra: Applications to Irradiated Crystals of Malonamide and Glycine

The electron spin resonance spectrum resulting from the anisotropic coupling with one proton is known to consist of two doublets whose splittings and intensities depend on frequency as well as orientation of the magnetic field. The possible appearance of both doublets in the same spectrum can be used to aid the analysis of complicated spectrum. It is used here to establish the existence of more than one radical species in irradiated malonamide and to verify the H(C) coupling constants in NH3+(ĊH)CO2— that were reported earlier by Ghosh and Whiffen in γ-irradiated glycine. A hyperfine coupling tensor having principal values of −29, −59, and −89 Mc/sec was observed in γ-irradiated malonamide and used to identify the radical ĊH(CONH2)2 with the spin density concentrated in a p-orbital of the central carbon atom. The theory of anisotropic magnetic hyperfine interactions is extended to include coupling cases other than a single nucleus with spin ½ and the experimental conditions required for observation of more than the usual 2I+1 hyperfine lines are examined.