NMR MEASUREMENT OF SPIN-3/2 TRANSVERSE RELAXATION IN AN INHOMOGENEOUS-B(1) FIELD

Biexponential transverse relaxation of spin-3/2 nuclei is routinely measured using either a spin echo or a multiple-quantum filtration NMR experiment. If the flip angle of the refocusing pulse used in these experiments deviates from 180-degrees then the measured relaxation appears to be triexponential, with the relative amplitudes of the three components showing a strong flip angle dependence. This has important implications for relaxation measurements where, as a result of inhomogeneity of the B1 radiofrequency field, there is a distribution of flip angles across the sample. A new experiment is demonstrated in which the measured spin-3/2 transverse relaxation also appears to be triexponential but where the relative amplitudes of the three components are independent of flip angle.