%0 Journal Article %J Journal of Magnetic Resonance Series A %D 1993 %T Effects of Double Rotation on Homonuclear Spin Systems %A Wu, Y. %A Peng, Z. Y. %A Olejniczak, Z. %A Sun, B. Q. %A Pines, A. %K solids %B Journal of Magnetic Resonance Series A %V 102 %P 29-33 %8 Mar %@ 1064-1858 %G English %U ://WOS:A1993KZ35400005 %N 1 %M WOS:A1993KZ35400005 %! Effects of Double Rotation on Homonuclear Spin Systems %R Doi 10.1006/Jmra.1993.1064 %0 Journal Article %J Catalysis Letters %D 1992 %T Adsorption Effects in Aluminophosphate Molecular-Sieves Studied by Al-27 Double-Rotation Nmr %A Jelinek, R. %A Chmelka, B. F. %A Wu, Y. %A Davis, M. E. %A Ulan, J. G. %A Gronsky, R. %A Pines, A. %K alpo4-8 %X

Al-27 double rotation NMR (DOR) spectroscopy is used to investigate structural changes in the framework of several aluminophosphate molecular sieves upon adsorption of water. The shapes, widths, and positions of the spectral lines yield information on the aluminum environments, adsorption sites, and degree of structural disorder undergone upon water adsorption.

%B Catalysis Letters %V 15 %P 65-73 %@ 1011-372X %G English %U ://WOS:A1992JJ25900008 %N 1-2 %M WOS:A1992JJ25900008 %! Adsorption Effects in Aluminophosphate Molecular-Sieves Studied by Al-27 Double-Rotation Nmr %R Doi 10.1007/Bf00770899 %0 Journal Article %J Solid State Nuclear Magnetic Resonance %D 1992 %T Sidebands in dynamic angle spinning (DAS) and double rotation (DOR) NMR %A Sun, B. Q. %A Baltisberger, J. H. %A Wu, Y. %A Samoson, A. %A Pines, A. %K central transition %X

A theory of dynamic angle spinning (DAS) and double rotation (DOR) NMR is described using average Hamiltonian and irreducible tensor methods. Sideband intensities in DAS and DOR spectra are analyzed by both the moment and Bessel function methods, and general formulae are derived. Results show that the DAS moments depend on the relative rotor phase between the first and the second evolution periods, whereas the second and third DOR moments are independent of the relative phase between the inner and outer rotors. Sideband intensities in DAS spectra also depend on the relative rotor phases between evolution at the first and second angles, as well as on the ratio of time spent at each angle. Sideband intensities and phases in DOR spectra are related to the relative rotor phases between the inner and outer rotors, and the sideband pattern is determined by the ratio of the inner and outer rotor spinning speeds. An inversion symmetry of the odd numbered DOR sidebands at the relative rotor phase gamma(r) = 0 degrees. 180 degrees permits the elimination of these sidebands. Finally, numerical simulations are implemented and shown to agree with experimental results. Quadrupolar parameters can therefore be recovered either by calculating the second and third moments or by simulating the sideband intensities and phases.

%B Solid State Nuclear Magnetic Resonance %V 1 %P 267-295 %8 Dec %@ 0926-2040 %G English %U ://WOS:000208537400006 %N 5 %M WOS:000208537400006 %! Sidebands in dynamic angle spinning (DAS) and double rotation (DOR) NMR %R Doi 10.1016/0926-2040(92)90047-D %0 Conference Paper %D 1991 %T Framework ordering in aluminophosphate molecular sieves studied by (27)Al double rotation NMR %A Chmelka, B.F. %A Wu, Y. %A Jelinek, R. %A Davis, M.E. %A Pines, A. %E P.A. Jacobs, N.I. Jaeger, L. Kubelkova, and B. Wichterlov %I Elsevier %V 69 %P 435-442 %8 1991 %G eng %0 Journal Article %J Journal of the American Chemical Society %D 1991 %T High-Resolution O-17 Nmr of Solid Silicates %A Mueller, K. T. %A Wu, Y. %A Chmelka, B. F. %A Stebbins, J. %A Pines, A. %K spectra %X

Several O-17-enriched silicates were studied by use of dynamic angle spinning (DAS) and double rotation (DOR) nuclear magnetic resonance spectroscopy. These methods average away second-order quadrupolar interactions by reorienting a sample about a time-dependent axis, thereby yielding high-resolution spectra of oxygen-17 nuclei. A narrow spectral line is observed for each distinct oxygen site at the sum of the isotropic chemical shift and the field-dependent isotropic second-order quadrupolar shift. Resolution is increased by up to 2 orders of magnitude compared to conventional magic angle spinning (MAS) spectra. Crystallographically inequivalent oxygens are now observable as distinct resonances in spectra of polycrystalline silicates such as diopside (CaMgSi2(17)O6), wollastonite (CaSi17O3), clinoenstatite (MgSi17O3), larnite (Ca2Si17O4),and forsterite (Mg2Si17O4).

%B Journal of the American Chemical Society %V 113 %P 32-38 %8 Jan 2 %@ 0002-7863 %G English %U ://WOS:A1991ER08200006 %N 1 %M WOS:A1991ER08200006 %! High-Resolution O-17 Nmr of Solid Silicates %R Doi 10.1021/Ja00001a006 %0 Journal Article %J Journal of the American Chemical Society %D 1991 %T Study of the Aluminophosphates Alpo4-21 and Alpo4-25 by Al-27 Double-Rotation Nmr %A Jelinek, R. %A Chmelka, B. F. %A Wu, Y. %A Grandinetti, P. J. %A Pines, A. %A Barrie, P. J. %A Klinowski, J. %K nuclei %X

Aluminum-27 double-rotation NMR in a magnetic field of 11.7 T distinguishes the extremely distorted five-coordinated aluminum sites in the molecular sieve precursor ALPO4(-21). Upon calcination, ALPO4(-21) transforms to ALPO4(-25), which has two tetrahedral aluminum sites with similar isotropic chemical shifts that cannot be resolved in an 11.7 T field. The two tetrahedral environments, however, have a different quadrupole coupling constants and are distinguished by double rotation at 4.2 T field. The quadrupole coupling constants obtained for these sites indicates that the tetrahedral aluminum environments are less distorted in the hydrated material.

%B Journal of the American Chemical Society %V 113 %P 4097-4101 %8 May 22 %@ 0002-7863 %G English %U ://WOS:A1991FN00500007 %N 11 %M WOS:A1991FN00500007 %! Study of the Aluminophosphates Alpo4-21 and Alpo4-25 by Al-27 Double-Rotation Nmr %R Doi 10.1021/Ja00011a007 %0 Journal Article %J Nature %D 1990 %T High-Resolution Al-27 Nmr-Spectroscopy of the Aluminophosphate Molecular-Sieve Vpi-5 %A Wu, Y. %A Chmelka, B. F. %A Pines, A. %A Davis, M. E. %A Grobet, P. J. %A Jacobs, P. A. %B Nature %V 346 %P 550-552 %8 Aug 9 %@ 0028-0836 %G English %U ://WOS:A1990DT67900067 %N 6284 %M WOS:A1990DT67900067 %! High-Resolution Al-27 Nmr-Spectroscopy of the Aluminophosphate Molecular-Sieve Vpi-5 %R Doi 10.1038/346550a0 %0 Journal Article %J Journal of Magnetic Resonance %D 1990 %T Nmr Experiments with a New Double Rotor %A Wu, Y. %A Sun, B. Q. %A Pines, A. %A Samoson, A. %A Lippmaa, E. %B Journal of Magnetic Resonance %V 89 %P 297-309 %8 Sep %@ 0022-2364 %G English %U ://WOS:A1990DU81300008 %N 2 %M WOS:A1990DU81300008 %! Nmr Experiments with a New Double Rotor %R Doi 10.1016/0022-2364(90)90236-3 %0 Journal Article %J Spectroscopy %D 1990 %T Nuclear Magnetic Resonance %A Pines, A. %A Wu, Y. %B Spectroscopy %V 5 %P 34-35 %G eng %N 9 %! Nuclear Magnetic Resonance %0 Journal Article %J Nature %D 1989 %T O-17 Nmr in Solids by Dynamic-Angle Spinning and Double Rotation %A Chmelka, B. F. %A Mueller, K. T. %A Pines, A. %A Stebbins, J. %A Wu, Y. %A Zwanziger, J. W. %B Nature %V 339 %P 42-43 %8 May 4 %@ 0028-0836 %G English %U ://WOS:A1989U445100054 %N 6219 %M WOS:A1989U445100054 %! O-17 Nmr in Solids by Dynamic-Angle Spinning and Double Rotation %R Doi 10.1038/339042a0