Transverse relaxation times of spin 3/2 nuclei in the quadrupole nutation NMR experiment.

Transverse relaxation times in the rotating frame of quadrupolar nuclei with half-integer spins are inversely proportional to the linewidth of quadrupole nutation NMR spectra. We apply fictitious spin -1/2 operators to I = 3/2 nuclei to derive correlations between the transitions of a multi-level system which affect nuclear relaxation. When omega rf << omega Q, all possible multiple-quantum transitions contribute to the transverse quadrupolar relaxation time in the rotating frame T2Qp. When omega rf >> omega Q, two of the three single-quantum transitions do not contribute. In the low-temperature region (outside the extreme narrowing limit), the contribution of double- and triple-quantum coherences to T2Qp goes through a minimum for omega rf << omega Q, while the triple-quantum coherence appears at zero frequency and corresponds to a short transverse relaxation time for omega rf >> omega Q.