H-1 ENDOR INVESTIGATIONS ON GAMMA-IRRADIATED BETAINE CALCIUM-CHLORIDEDIHYDRATE IN THE INCOMMENSURATE PHASE

The electron nuclear double resonance (ENDOR) technique is applied to study the influence of the incommensurate modulation on the proton hyp erfine structure (hfs) tensors of the (N) over dot(CH3)(3) radical in betaine calcium chloride dihydrate (BCCD). The temperature dependence of the edge singularities due to the increasing of the incommensurate (IC) modulation amplitude could be observed in the H-1 ENDOR of the CH 3 groups for the first time. The rotation pattern of the edge singular ities observed in the H-1 spectra in the IC phase of BCCD can be expla ined by a libration around the C-1-N axis with a tilt angle of about /-7 degrees.