Broadband decoupling in NMR with frequency-modulated ‘chirp’ pulses

In NMR of spins with I = 12 in an isotropic phase, it is demonstrated by simulation and experiment that virtually unlimited bandwidths can be decoupled effectively by using chirp pulses with linear frequency modulation for adiabatic inversion combined with phase-cycles and supercycles similar to those used in composite pulse decoupling. The average radio-frequency amplitude required is modest compared to other techniques. In applications with inhomogeneous radio-frequency (RF) fields, as in magnetic resonance imaging and localized spectroscopy with surface coils, the RF amplitude can be apodized at the rising and falling edges of chirp pulses to improve adiabatic behavior.