Electron Spin Resonance Study of Radical Pairs Trapped in X-Irradiated Single Crystals of Dimethylglyoxime-O,O-d2, Glyoxime, and Methylglyoxime at Liquid-Nitrogen Temperature

The ESR spectra of x‐irradiated single crystals of dimethylglyoxime‐O,O‐d₂, glyoxime, and methylglyoxime have been measured at 77°K. An analysis of the spectra reveals the presence of radical pairs R₁—CR₂NȮ···R₁—CR₂NȮ , where R₁=C(CH₃)NOD and R₂=CH₃ for dimethylglyoxime‐d₂ (the average distance between the unpaired electrons R=5.4 Å), R₁=CHNOH and R₂=H for glyoxime ($\mathrm{R}\text{≦4.8}$ Å), and R₁=CHNOH and R₂=CH₃ for methylglyoxime ($\mathrm{R}\text{≦5.2}$ Å). Radical pairs decay in dimethylglyoxime faster than in dimethylglyoxime‐d₂. The fact shows that the iminoxy radicals CR₁NOH–CR₂NȮ diffuse by hydrogen‐atom abstraction from nearby hydroxyl groups.