COMPARISON OF THE COHERENCE-TRANSFER EFFICIENCIES OF LABORATORY-FRAME AND ROTATING-FRAME EXPERIMENTS

Coherence transfer under INEPT and isotropic mixing is quantified theoretically and the predictions are verified by experiments on various homonuclear spin systems. A general expression for magnetization transfer is derived for INEPT in AMXN systems, in terms of the "leaving fraction," trigonometric function, "spin multiplier," and "attenuation factor." In general, coherence transfer under INEPT is not identical from AM to XN and XN to AM when M ≠ N. Unlike INEPT, in the case of isotropic mixing all magnetization components are conserved for the spin system as a whole, transfer is in-phase, and the m = 0 component of spin multiplets also plays a role in coherence transfer, leading to advantages over INEPT under conditions of unresolved couplings and integer composite angular momenta. Coherence-transfer efficiencies of these experiments are compared with the predicted universal bound on spin dynamics. © 1992.