Solvent suppression jump-return

Special pulses containing one or several notches in their excitation profiles have been designed for purposes of solvent suppression. Obviously such pulses could be used also for suppression of parent lines in applications involving isotopi-cally diluted nuclei. One of the simplest experiments of this kind is the jump and return experiment [24] and corresponding higher order binomial pulses with alternating phases. Similarly to binomial excitation pulses these constant amplitude solvent suppression pulses create sidebands and excitation sidelobes. Corresponding amplitude modulated pulses [25,26] provide a better alternative. 

Filter elements have been developed, not just for coupling evolution, but also for chemical shift selection [5.215 - 5.221]. An early example was the jump-return method for solvent signal suppression. Check it 5.2.3.3, whereby the resonances at a given chemical shift and related multiples were suppressed. In common with the z-filter for zero-quantum suppression, the CSSF (Chemical 5hift iSelective Filter) element uses different free precession periods to give varying degrees of chemical shift evolution for each scan in a multiple scan experiment. 

A wide range of other methods for solvent suppression has been developed which may collectively be classed as tailored excitation. These rely on the application of appropriate combinations of pulses to excite protons lying outside a narrow band of frequencies while leaving those within that band (i.e. the solvent) undisturbed. Examples of these are the Redfield pulse [38], the jump-return technique [39] and binomial sequences [40]. 

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