Coherence sidebands in adiabatic decoupling

RF pulse sequences applied to IS spin systems may produce substantial transverse antiphase S magnetization coupled to antiphase I magnetization, just prior to detection of the S signal, for samples containing a range of J coupling constants, or when pulse sequence delays are misset from ideal values, This magnetization is generally considered to be unobservable. Adiabatic decoupling on the I spins during signal detection efficiently converts this magnetization to observable S signal in the form of sidebands which we dub "coherence sidebands." Three single-transient pulsed-field-gradient methods are described for eliminating these unwanted sidebands, The techniques are applicable to H-1-detected C-13-decoupled experiments on spectrometers operating at a H-1 frequency of up to 2 GHz. (C) 1997 Academic Press.