STUDY OF SLOW MOLECULAR MOTIONS IN SOLUTION USING OFF-RESONANCE IRRADIATION IN HOMONUCLEAR NMR .1. LONG DIPOLAR CORRELATION TIMES

We have investigated the effects of overall tumbling motions with char acteristic times greater than 0.1 mu s on the dipolar relaxation in th e presence of an off-resonance rf irradiation. The relaxation rates de pend on the effective field amplitude in the rotating frame, and there fore on the rf field strength and offset (giving access to a large dom ain of characteristic times). Different methods for detecting and meas uring this phenomenon, using off-resonance ROESY and local effective c orrelation time measurement are described. They are essentially based on a variation of the rf field amplitude at constant angle 0 between t he effective field and the static magnetic field. An application to gl ycogen is presented.