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Recent experimental developments of high-resolution NMR in solids (for example, double rotation and dynamic-angle spinning) address the reduction of second-order line broadening effects, particularly in systems involving quadrupolar nuclei such as 23Na, 17 0, 27 AI, and 14N. However, some aspects of the theoretical description of these systems have not been clearly understood; in particular, the various procedures available to truncate the interactions give incompatible results. We present a general framework, based on static perturbative methods, which provides a natural procedure to derive the correct Hamiltonian for higher-order effects in irreducible tensor form. Applications of this method to coherent averaging techniques (sample motion or radio-frequency irradiation) are described and compared to previous treatments based on average Hamiltonian theory.

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We dedicate this paper to Prof. Dr. Werner Müller-Warmuth on the occasion of his 65th birthday. Z. T. L. and U. H. owe much to his advice.We report the first single crystal deuteron NMR spectra of CD3 groups which display the socalled ±ß, ± (|a| ± ß) and ±(2|a| ± ß) lines characteristic of rotational tunneling in a sufficiently clear manner to allow a quantitative comparison with the respective theory developed in 1988 by the group of W. Müller-Warmuth. The molecular system we study is aspirin-CD3. We recorded spectra for differently oriented single crystals and measured spin-lattice relaxation times T\ in a wide temperature range. At 12.5 K we exploit the dependence of the ±(|a| ± ß) and ±(2|a| ± ß) lines on the orientation of the applied field Bo for determining the equilibrium orientation of the CD3 group in the crystal lattice. The spectra display features which allow, by comparison with simulated spectra, a measurement of the tunnel frequency ut. Its low temperature limit is (2.7 ± 0.1) MHz. It allows to infer the height V3 of the potential V(

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The unilamellar form of zeolite MWW, MCM-56, which is obtained by direct hydrothermal synthesis has been studied with regard to acidity and porosity in its original and post-synthesis modified pillared and delaminated forms. The acidity measured by FTIR was found to be only slightly lower than the highly active 3-D MWW forms, MCM-22 and MCM-49. Pivalonitrile adsorption, which is a measure of spatial openness, showed 50% accessibility vs. <30% for MCM-22/49. It highlights the potential of MCM-56 as a layered material with increased access to acid sites because it does not entail laborious post-synthesis modification. Swelling, pillaring and delamination of MCM-56 are facile but result in a reduction in the number of Brønsted acid sites (BAS) while increasing accessibility to pivalonitrile. The delamination procedure involving sonication and acidification of the highly basic mother liquor produces the most visible increase in surface area and access to all BAS. The accompanying doubling of the solid yield and the decrease in absolute number of BAS suggest significant precipitation of dissolved silica generated during swelling and sonication in high pH medium. The viability of separating surfactant covered layers upon sonication with the consequence of exposing hydrophobic hydrocarbon tails to aqueous environment is addressed.