Magic-angle

Figure Bl.6.12 Ionization-energy spectrum of carbonyl sulphide obtained by dipole (e, 2e) spectroscopy [18], The incident-electron energy was 3.5 keV, the scattered incident electron was detected in the forward direction and the ejected (ionized) electron detected in coincidence at 54.7° (angular anisotropies cancel at this magic angle ). The energy of the two outgoing electrons was scaimed keeping the net energy loss fixed at 40 eV so that the spectrum is essentially identical to the 40 eV photoabsorption spectrum. Peaks are identified with ionization of valence electrons from the indicated molecular orbitals.

Disadvantages. The magic angle must be extremely stable and accurately set. The spiiming speed must show good stability over the duration of the experiment. The probe needs to be accurately tuned and careful correction for irradiation and detection variations with frequency, and baseline effects are necessary. The gain... 

NMR has developed into a powerfiil analytical teclmique in the past decades, and has been used extensively in the characterization of a great number of chemical systems. Its extension to the study of surfaces, however, has been hampered by the need of large samples because of its poor sensitivity. On the otiier hand, the development of magic-angle-spiiming NMR (MAS-NMR) and the extension of NMR to many nuclei besides... 

Chemical shift (isotropic component) 5. ISO Magic-angle spinning Chemical bonding coordination number... 

Figure 6 Solid state static and magic-angle spinning NMR spectra of a-Mg2V2(>7.

Nuclear Magnetic Resonance Magic-Angle Spinning... 

Solid-state Alnmr spectroscopy has been much used in recent years to study the composition and structure of aluminisilcates (pp. 351 -9) and other crystalline or amorphous Al compounds. The technique of magic angle spinning (MAS) must be used in such cases. ... 

J. w. Geus, The interlayer collapse during dehydration of synthetic Na -beidellite a %a solid -state magic-angle spinning NMR study. Clays Clay Minerals. 25 457 (1992). 

Lindberg, J. J. and Hortling, B. Cross Polarization — Magic Angle Spinning NMR Studies of Carbohydrates and Aromatic Polymers. Vol. 66, pp. 1—22. 

As a consequence of restricted internal mobility in molecules in the crystalline state, nuclei in different conformation environments, but identical in other respects, can produce different signals in 13C cross polarization, magic angle spinning (CPMAS) solid-state NMR. This analysis is not necessarily limited to crystalline regions, since signals of different conformations are resolved if the exchange is slow with respect to the time scale of the NMR experiment. 

Sometimes decomposition reactions can be avoided by carrying out diazotizations in concentrated sulfuric acid. By this method Law et al. (1991) obtained the 1,5-bisdiazonium salt (incorrectly called tetrazonium salt) of l,5-diamino-4,8-dihy-droxy-anthraquinone, which is deprotonated to 2.28. The structure was verified by cross-polarization magic angle spinning (CPMAS) 13C NMR spectroscopy. 

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