Field gradient artifact suppression

The use of actively shielded magnetic field gradients has made the use of pulsed field gradients possible. The use of pulsed field gradients reduces experiment time, minimizes artifacts, and allows for further solvent suppression. 

Pulsed field gradients are added to existing NMR pulse sequences in order to suppress artifacts and/or to select certain coherence transfer pathways. The application of gradients for these two purposes maintain different requirements and benefits. 

Before the development of pulsed field gradient sequences (see below), most NMR pulse sequences included a phase cycle in which the phases of at least one pulse and the receiver were varied systematically. This was needed for one or more of several reasons, e.g. suppression of unwanted signals, suppression of artifacts due to hardware imperfections and/or incomplete return to equilibrium between scans and coherence pathway selection in multidimensional NMR. One example of each the first two kinds of phase cycle is briefly discussed below. 

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