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It was found that the ENDOR signal from a weakly interacting radical was negative while that from a relatively strongly interacting radical was positive; in crystals with very low doses, intensity of a strong negative ENDOR line was comparable with that of the original ESR line.

The charge transfer in acetonitrile-halogen complexes was examined by means of the nuclear quadrupole resonances resulting from the relevant nuclei. 14N NQR parameters (|e2Qq|=3.6000 MHz and η=0.0183) and 35Cl NQR parameters (|e2Qq|=107.44 and 108.50 MHz) were obtained for the acetonitrile-chlorine complex, whereas 14N NQR parameters (|e2Qq|=3.5439 MHz and η=0.0043) and a 81Br NQR parameter (|e2Qq|=640.52 MHz) were obtained for the acetonitrile-bromine complex. From these parameters, the charged states of the nitrogen, chlorine, and bromine atoms in these charge-transfer complexes were calculated by means of the Townes and Dailey theory. In the case of the acetonitrile-bromine complex, the charge loss at the nitrogen atom was not equal to the gain at the bromine atom, as long as the charge was assumed to be transferred only to the p-orbital of the latter. This discrepancy was explained by assuming some d-hybridization at the bromine atom. The charged states of the nitrogen atoms in these complexes were qu...