Composite pulses broadband decoupling

Composite pulses have also been used in overcoming problems due to sample overheating during broadband decoupling experiments. A widely used pulse sequence is Waltz-16 (Shaka et al., 1983), which may be repre-... 

Composite pulses reduce the error introduced due to the delay between the start of the pulse and when it reaches full power. They have also been used to overcome problems of sample overheating during broadband decoupling and in experiments in which pulses have to be applied for long durations. 

H and 19F NMR spectra are recorded with a normal one-pulse sequence or, alternatively, the XH spectra are recorded with a sequence that allows simultaneous solvent suppression with presaturation (31) or a sequence that includes some other method of suppression 13C 1H and 1P 1H spectra are recorded with proton broadband (composite pulse) decoupling (32), and 31P spectra with gated proton decoupling (33). 

Multiple-pulse sequences are indispensable tools for the practical implementation of Hartmann-Hahn experiments in liquid state NMR. They often consist of thousands of defined rf pulses with or without intermediate delays and allow one to create a desired form of the effective Hamiltonian for a given class of spin systems. In the field of high-resolu-tion NMR, multiple-pulse sequences are also used for broadband het-eronuclear decoupling (Levitt et al., 1983 Shaka and Keeler, 1986). Composite pulses (Levitt, 1986) and shaped pulses (Warren and Silver, 1988 Freeman, 1991 Kessler et al., 1991) may be considered as special classes of multiple-pulse sequences. 

Table 9.2. Selected composite-pulse sequences for broadband decoupling and spin-locking...

Even better homonuclear Hartmann-Hahn transfer can be achieved (Bax and Davis, 1985b) when broadband heteronuclear decoupling schemes such as MLEV-16 (Levitt et a/., 1982) and WALTZ-16 (Shaka et al 1983a, b) are employed, which are based on composite 180° pulses (Levitt et al., 1983 Barker et al., 1985 Shaka and Keeler, 1987). 

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