Electron Spin Resonance of an Irradiated Single Crystal of Deuterated DL-Tartaric Acid

The electron spin resonance spectra of an irradiated single crystal of DL-tartaric acid grown from water was found to be complex, but the spectra of a deuterated single crystal could be analyzed and the nature of the free radical ascertained. Measurements were made at 9 and at 23 kMc/sec. For some orientations of the crystal in the external magnetic field an unresolved doublet was observed with weak satellite lines separated by 5 gauss at 9 kMc/sec and by 13 gauss at 23 kMc/sec. These satellite lines evidently arise from second-order transitions. From the analysis we suggest that the free radical is probably[Complex chemical formula]with the unpaired spin on a carbon atom. The principal values of g are 2.0025, 2.0026, and 2.0047. The principal elements of the nuclear coupling of the CH protons are ∓0.2, ±1.1, and ±6.5 gauss.