It is known that the patterns of spinning sidebands observed in Multiple spinning sidebands are frequently observed in the multiple-quantum dimension of MQMAS spectra are often the MQMAS spectra. Their number is usually much greater significantly wider than expected from the anisotropies of relevant along the multiple-quantum (n 1 ) than along the single-quaninteractions. It has been recently shown by others that these sidetum (n 2 ) dimension. More importantly, however, the overall bands are generated due to the rotor-driven reorientations that the width of the sideband pattern along n 1 often exceeds the quadrupole tensors of the crystallites undergo during the evolution spectral range expected from direct rotational modulation of period between the multiple-and single-quantum conversion prothe interaction anisotropies during t 1 , which is the ''classicesses. We present an experimental and theoretical study of the cal'' origin of spinning sidebands in solid-state NMR. This effects of the spinning speed n R and RF field strength n RF on the phenomenon was recently reported and analyzed by Madevelopment of these sideband patterns. The theoretical analysis rinelli and Frydman (10), who concluded that it was due to relies upon numerical simulations and includes propagation of the density matrix during the entire MQMAS experiment. The rotor-driven reorientations that the quadrupole tensors of the possibility of additional rotational encoding during the RF pulses crystallites undergo during the evolution period between the is discussed. Both the theoretical and experimental results show two H pulses. In their study, the MQMAS spectrum was the benefits of using the highest available n R and n RF . α§ 1998 calculated analytically from the powder-averaged evolution Academic Press