Electron Spin Resonance in an Irradiated Single Crystal of Dimethylglyoxime

The paramagnetic resonance of gamma‐irradiated single crystals of dimethylglyoxime has been measured at 23 kMc/sec and 9 kMc/sec for various orientations of the crystal in the magnetic field. The resonance pattern was found to have a triplet structure caused by coupling to a single N¹⁴ nucleus. Both the nuclear coupling and the spectroscopic splitting factor were found to be anisotropic with the principal values; A₁=45±1 gauss, A₂=A₃=25±1 gauss, g₁=2.0026±0.0003, g₂=2.0063±0.0003, and g₃=2.0095±0.0003. It is concluded that the free radical produced by the irradiation is probably the ionized dimethylglyoxime molecule, $${}_{{\mathrm{CH}}_3–}^{\mathrm{H}\mathrm{¨–}\mathrm{O}–\mathrm{N}=}\mathrm{C}–{\mathrm{C}}_{={\mathrm{N}}^{+}–\mathrm{O}–\mathrm{H},}^{–{\mathrm{CH}}_3}$$ with the positive charge and the electron spin density concentrated on one of the nitrogens and in an hybridized sp² orbital which is approximately in the molecular plane and along the bisector of the C=N–O angle. The s character in the orbital is calculated from the N¹⁴ coupling to be 19%.