Paramagnetic Resonance of X-Irradiated Single Crystals of Rochelle Salt

The electron-spin resonances of single crystals of Rochelle salt and deuterated Rochelle salt irradiated with 40 kv x rays have been studied as a function of orientation of the crystal in the magnetic field. The spectra are time dependent, and by studies of the decay of the spectra it has been found that three kinds of centers are present. In Rochelle salt one of these gives rise to an intense doublet which decays rapidly, another to a doublet which grows and then decays, and the third is an eight-line spectrum which grows and is stable. It is shown that the waters of hydration play an important role in the kinetics of the growth and decay of the centers. The stable spectrum has been analyzed, and it is concluded that two of the lines arise from breaking one of the C–H bonds. This doublet is slightly anisotropic, and arises from hyperconjugation to the proton on the adjacent carbon, and dipolar coupling between it and the large spin density on the carbon. A second pair of lines arises from breaking the other C–H bond, and since the hydrogens are not equivalent, this pair has a different splitting. The other two pairs are shown to be couplings to either OH or water of hydration hydrogens.