A new method for separating isotropic and anisotropic chemical-shift interactions in magic-angle-spinning NMR is presented. The new method is based upon manipulation of the phases of spinning sidebands using sequences of five π pulses. A two-dimensional pulse scheme separates the spinning sidebands by order. The amplitudes of the spinning sidebands may be analyzed to obtain the principal values of the chemical-shift anisotropy. For sites with many sidebands, it is possible to improve the signal-to-noise ratio considerably by skew projection of the two-dimensional spectrum. Experimental demonstrations are presented.
Upprättat; 1995; 20070416 (bajo)