Fast proton spin-lattice relaxation time in the rotating frame during the application of time averaged precession frequency

A relatively rapid phase alternation of the effective field in the time averaged precession frequency (TAPF) sequence results in averaging of the proton RF spin-lock field. The spin-locking of the proton magnetization becomes less efficient and thus shortens T1ρH, the proton spin-lattice relaxation time in the rotating frame. The relaxation time also depends on the ratio of τ1 and τ2 intervals i.e. τ1/τ2 and not only on the number of τc = τ1 + τ2 blocks, i.e. the number of the phase transients. Experiments are performed on solid samples of ferrocene and glycine and for some time intervals, T1ρH is shortened by factors of 9-100 compared to the relaxation times obtained in the standard experiment.