The effect of experimental imperfections on TOSS spectra

The effect of imperfections on the TOSS experiment, used to suppress rotational sidebands in magic-angle-spinning NMR, is examined. We consider the effects of errors in pulse lengths, phases, and timing as well as resonance offset effects. Errors in the phases of the π pulses have no effect on the efficiency of sideband suppression, and only introduce a phase shift into the spectrum. In contrast, errors in the length of the π pulses or in their timing lead to an attenuated center-band as well as the reintroduction of residual sidebands. Our results show that phase alternation of the π pulses does not necessarily compensate for pulse length errors and can, in fact, exacerbate their effects. The use of composite π pulses in TOSS is briefly examined and is shown to yield superior performance for spectral lines far from resonance.