We present robust radio frequency (rf) pulses that tolerate a factor of sixinhomogeneity in the B1 field, significantly enhancing the potential of toroidcavity resonators for NMR spectroscopic applications. Both point-to-point (PP)and unitary rotation (UR) pulses were optimized for excitation, inversion, andrefocusing using the gradient ascent pulse engineering (GRAPE) algorithm basedon optimal control theory. In addition, the optimized parameterization (OP)algorithm applied to the adiabatic BIR-4 UR pulse scheme enabled ultra-short(50 microsec) pulses with acceptable performance compared to standardimplementations. OP also discovered a new class of non-adiabatic pulse shapeswith improved performance within the BIR-4 framework. However, none of theOP-BIR4 pulses are competitive with the more generally optimized UR pulses. Theadvantages of the new pulses are demonstrated in simulations and experiments.In particular, the DQF COSY result presented here represents the firstimplementation of 2D NMR spectroscopy using a toroid probe.
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