Abstract: The transverse relaxation of nuclear spin systems deviates significantly from exponential or multiexponential decay as usual relaxation theory predicts NMR spectroscopy. The transverse magnetization of the nuclear spins decays much slower at long times (typically thousand microseconds) than at the initial stage (tens of microseconds) and gives rise to long time tail (LTT) effect on the transverse relaxation. The long time tail effect in liquid state NMR spectroscopy has been explored and characterized. Its applications have been proposed for the improvement of resolution and line narrowing in NMR spectroscopy. Mainly the resolution is enhanced at later stage of relaxation rather than at the earlier stage. It is found that the physical mechanism for the long time tail of the spin autocorrelation function in the liquid state is similar to, but not identical with, that in the solid state. The long time decay rate depends on both the local details and overall characteristics of the spin interactions. LTT effect on line narrowing in liquid state NMR spectroscopy has been demonstrated on some model compounds as a novel alternative technique to enhance resolution.

Keywords: NMR, Transverse relaxation, Spectroscopy, Long time tail effect.