DYNAMIC H-2 NUCLEAR-MAGNETIC-RESONANCE OF ROTATING SOLIDS

The sensitivity of one-dimensional dynamic magic-angle spinning (MAS) and off-MAS H-2 nuclear magnetic resonance spectra to changes in the p arameters of jump-type molecular motions is studied. The Floquet theor y approach is used to simulate spectra of spins with I = 1, which are involved in exchange processes in rotating solids. The solution of the Bloch-McConnell equations for rotating samples are derived and some s imulated frequency spectra are shown. The dependence of the lineshapes of the center and sidebands of the MAS and off-MAS spectra on the exc hange parameters are discussed. Experimental results of H-2 spectra of perdeuterated dimethyl sulfone, obtained in the temperature range 20- 55 degrees C, are demonstrated. The methyl groups in this molecule und ergo pi flips at rates that can be detected by MAS and off-MAS NMR. Th e shapes of the experimental sidebands are compared with simulated res ults.