We introduce a new family of pulse sequences, which have the effect of suppressing rotational sidebands in magic-angle spinning spectra. The sequences are based on the principle of suppressing evolution of the magnetization during certain timed fractions of the rotor cycle. Evolution during the intervening intervals causes destructive interference of the Fourier components which lead to sidebands. Evolution is suppressed using pairs of hard RF pulses of equal intensities and opposite phase. The sequences are shorter and more robust than previous methods, and can be designed to incorporate refocusing pulses. Experimental details, examples, and criteria for optimization are provided.
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