Transverse relaxation times of spin [formula omitted] nuclei in the quadrupole nutation NMR experiment

Abstract

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 ω rf ⪡ ω Q, all possible multiple-quantum transitions contribute to the transverse quadrupolar relaxatio time in the rotating frame T 2Q ϱ . When ω rf ⪢ ω 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 T 2Q ϱ goes through a minimum for ω rf ⪡ ω Q, while the triple-quantum coherence appears at zero frequency and corresponds to a short transverse relaxation time for ω rf ⪢ ω Q.