HETERONUCLEAR BROAD-BAND SPIN-FLIP DECOUPLING WITH ADIABATIC PULSES

The application of adiabatic pulses for heteronuclear broadband decoupling is described. It is shown that superior cyclicity can be achieved even when excitation-free intervals are inserted between successive pulses. Thanks to this feature, sample heating can be considerably reduced in comparison with the standard decoupling techniques with continuous irradiation, while the benefit of low sensitivity to RF field inhomogeneity is obtained. The peak power requirements depend not only on the decoupling bandwidth, but also on the parameters of the adiabatic pulses used. Generally, they correspond to the power requirements of broadband decoupling by WALTZ-16. Recommendations for the choice of a pulse suitable for a given application are presented. The intensity of cycling sidebands is the main trade-off of this method. Quantitative assessment of this intensity shows the limits for the pulse repetition period. Experimental verification on a 200 MHz spectrometer is described. (C) 1994 Academic Press, Inc.