The Meiboom—Gill Method

Such pulses can be used in place of the simple 90° and 180° pulses in most of the pulse sequences that we describe in this and later chapters. The trade-off of better effective rf homogeneity must be weighed in each instance against the additional complexity (which can usually be handled by modern spectrometers) and the extra time taken (which may not be acceptable in certain experiments). 

FIGURE 9.4 (a) Rotation of magnetization vectors in response to a 180, pulse.The vectors shown are off resonance, with (to — to /yB, ranging from 0.4 to 0.6. (b) Rotation of the same off-resonance magnetization vectors by a composite pulse, 90i240),90 produces much more effective inversion of the magnetization than the simple 180° pulse. From Freeman.19 

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