Satellite transition spectroscopy SATRAS

Portland cement and high-alumina cements contain, in addition to calcium silicate phases, calcium monoaluminate, CaAl204 (or CA in cement chemist s shorthand, where C = CaO and A = AI2O3). The Al NMR spectra of this compound, in which the Al is exclusively in tetrahedral coordination, and a number of other calcium alu-minates have been determined (Muller et al. 1986), and more recently, using satellite transition spectroscopy (SATRAS) which has allowed the multiple tetrahedral sites in the various calcium aluminates to be distinguished (Skibsted et al. 1993). The NMR parameters for the synthetic aluminates and a number of their hydration products are shown in Table 5.4. 

The satellite transition spectroscopy (SATRAS) approach, whereby the spectra of the satellite transitions are observed under MAS conditions and simulated to extract the relevant NMR information, is most generally applicable when the quadmpolar interaction is small. Shown in Figure 5 is an example of the spectra obtained by Trill et al. for a series of halide sodalites. " This method will also benefit from continued increases in available MAS rates. 

Other relevant methods are (1) quadrupole nutation spectroscopy, a two-dimensional technique which allows the projection of the conventional spectrum in one dimension, and only quadrupolar information in the second frequency axis, (2) dynamic-angle spinning (DAS), in which the sample is spun sequentially rather than simultaneously (as in DOR) about two different magic axes and (3) satellite transition spectroscopy (SATRAS), which monitors... 

Satellite Transition Spectroscopy (SATRAS) [9,10] has been proven to be a useful technique to determine the NMR parameters of quadrupolar spin systems, in particular when the quadrupolar frequency Uq is so small that the structure of the central transition (CT) 1/2 —1/2 due to second-order effects is not resolved. In that case, reliable informa-... 

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