ODESSA, a New 1D NMR Exchange Experiment for Chemically Equivalent Nuclei in Rotating Solids

A new 1D NMR exchange experiment in the slow-motion regime of spinning solids, with chemically equivalent nuclei exhibiting quadrupole coupling or chemical-shift anisotropy, is proposed. It consists of the usual three-pulse sequence for 2D exchange spectroscopy, P1-t1-P2-taum-P3-t-acquisition, but with the evolution time fixed at one-half a spinning period, t1 = TR/2, and a mixing time equal to an integer multiple thereof, taum = GTR. The magnetic polarizations associated with the various spinning sidebands are then polarized in alternate directions at the beginning of the mixing time. Dynamic processes during taum redistribute the polarizations, resulting in modified sideband patterns during the detection time, t. Experimental results are presented for carbon-13 and deuterium in dimethyl sulfone, which undergoes molecular reorientation in the solid state. The results are compared with simulations which include the effect of reorientation and longitudinal relaxation.