Magic-angle spinning, parameters

Wu has also reported solid-state Zn NMR spectra for ZnO, ZnS, ZnS04 7H20 and Zn(CH3COO)2. From the Zn NMR spectra obtained for stationary and magic-angle spinning (MAS) powder samples, useful parameters of chemical shift anisotropy (CSA)... 

Fig. 4. Quadrupolar powder patterns (a) Spin NMR powder pattern showing that the central -)<- ) transition is broadened only by dipolar coupling, chemical shift anisotropy, and the second-order quadrupolar interactions, (b) Spin 1 NMR powder pattern for a nucleus in an axially symmetric electric field gradient (see text). The central doublet corresponds to 6 = 90° in Eq. (10). The other features of low intensity correspond to 6 = 0° and 6 = 180°. (c) Theoretical line shape of the ) - -) transition of a quadrupolar nuclear spin in a powder with fast magic-angle spinning for different values of the asymmetry parameter t (IS) ...

We can successfully measure 170 MAS NMR spectra of poly(L-Ala)s using high-field and high-speed magic-angle spinning technique. From the 170 MAS spectra three kinds of NMR parameters such as chemical shift, quadrupolar coupling constant and asymmetric parameter were obtained exactly and understood the relationship... 

Spectra of solids arc complicated, because of the multiplicity of parameters involved, especially by anisotropic interactions as dipolar coupling. Many techniques both experimental or computational have been developed for interpretation. A technique particularly useful for catalysis permits to selectively suppress anisotropic contributions by mechanical rotation of the sample (magic angle spinning, MASNMR) and by rotation of the nuclear magnetic dipoles with sequences of radiofrcqucncy pulses. 

Solid-State NMR Spectroscopy. NMR Spectra. Structural information can also be obtained from the solid-state NMR spectroscopic analyses of the polysilylenes. In recording the solid-state spectra under conditions of magic angle spinning and cross polarization (27, 28), the experimental parameters can be varied to permit the observation of nuclei in distinct states of motion. We have reported the NMR spectra of PDHS in solution (2)... 

The now wide-spread use of solid state NMR techniques such as magic angle spinning (MAS) led to a need for calculations of NMR parameters such as chemical shifts and quadrupole coupling constants. A notable achievement this century has been the development of a method to calculate NMR chemical shielding in periodic solids. This will be described in the following section along with developments in the calculation of other properties. 

Fig. 3 The effect of slow magic-angle spinning. A set of spinning sidebands appears with a centre-band at the isotropic chemical shift and further lines spaced at the spinning frequency. The intensities of the sidebands change with spinning speed with higher-order sidebands (i.e., those further away from the centre-band) becoming less intense as the spinning speed increases. The chemical shift parameters used in the calculation of these sideband patterns are isotropic chemical shift offset 0 Hz chemical shift anisotropy 5 kHz asymmetry 0. Reproduced with permission from [16]...

Fig. 5 The effect of magic-angle spinning on the central transition lineshape for a half-integer spin quadrupolar nucleus. Left central transition lineshape under static, i.e., non-spinning conditions. Right the same transition under magic-angle spinning. The asymmetry parameter r is given with each spectrum. Reproduced with permission from [61])...

---