Elimination of the off-resonance effects

Typical 13C rectangular pulses with y Blmax = 20 kHz (12.5 and 25 /is for 90° and 180° pulses) generate large off-resonance effects for chemical shift range of 200 ppm required for 13C. These effects can lead to a significant attenuation or complete loss of signal in multi-pulse INADEQUATE pulse sequences. Practical implementations of INADEQUATE pulse sequences must, therefore, include some sort of compensation of off-resonance effects. Several approaches have been reported to date. 

Chirp pulses have also been used in a double-J-modulated INEPT-INADE-QUATE.29 Universal rotators constructed by combining two point-to-point rotations30 have been recently used in 1H- and 13C-detected IPAP-INADEQUATE experiments.31,32 

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