Constant amplitude broadband refocusing pulses from numerical optimization

Broadband refocusing pulses for high-field NMR can be constructed with broadband 90× pulses from numerical optimization of Bloch simulations concatenated with their time and phase reversed transformations. This work describes the search for minimal duration 18-kHz modulation frequency constant amplitude refocusing pulses made in this manner for bandwidths of 40, 60 and 80 kHz. Variants optimized at multiple frequencies and with sine squared amplitude truncation also are described. The resulting pulses are expected to have immediate application especially for (13)C refocusing in multidimensional experiments.