%0 Journal Article %J Journal of Physical Chemistry B %D 1997 %T Cross-polarization from quadrupolar nuclei to silicon using low-radio-frequency amplitudes during magic-angle spinning %A DePaul, S. M. %A Ernst, M. %A Shore, J. S. %A Stebbins, J. F. %A Pines, A. %K locking %X

The dynamics of cross-polarization from the central transition of a quadrupolar nucleus (Al-27 or Na-23) to a spin-1/2 nucleus (Si-29) during magic-angle spinning and using low-radio-frequency Geld strengths are analyzed for the mineral low albite. Under these conditions additional complications in the spin-lock behavior of the quadrupolar nucleus and in the cross-polarization process were found experimentally and are examined in detail. A step-by-step procedure for optimizing cross-polarization from the central transition of a quadrupolar nucleus to a spin-1/2 nucleus is described. Significant enhancement of Si-29 NMR sensitivity and several applications are demonstrated.

%B Journal of Physical Chemistry B %V 101 %P 3240-3249 %8 Apr 17 %@ 1089-5647 %G English %U ://WOS:A1997WU63000031 %N 16 %M WOS:A1997WU63000031 %! Cross-polarization from quadrupolar nuclei to silicon using low-radio-frequency amplitudes during magic-angle spinning %R Doi 10.1021/Jp9623711 %0 Journal Article %J Solid State Nuclear Magnetic Resonance %D 1997 %T Multiple-quantum magic-angle spinning and dynamic-angle spinning NMR spectroscopy of quadrupolar nuclei %A Wang, S. H. %A Xu, Z. %A Baltisberger, J. H. %A Bull, L. M. %A Stebbins, J. F. %A Pines, A. %K rb-87 %X

Several aspects of the Multiple-Quantum Magic-Angle Spinning (MQMAS) technique (L, Frydman and J,S, Harwood, J, Am, Chem, Sec., 117 (1995) 5367) are compared with Dynamic-Angle Spinning (DAS), Examples of MQMAS spectra are shown for I = 3/2 nuclei with C-Q up to 3.6 MHz, and for: Al-27 (I = 5/2) with C-Q up to 10 MHz. The MQMAS linewidth is largely independent of the magnitude of the homonuclear dipolar interaction, while the spinning sideband manifold is similar to that observed in DAS experiments, MQMAS is technically simple and routinely useful for studying nuclei with short spin-lattice relaxation times, but care must be taken in its use for quantitative studies as the excitation of the triple-quantum coherence is not uniform, In this regard, MQMAS is most useful for samples with small quadrupolar coupling constants, In the specific case of O-17, DAS would give spectra with excellent resolution in comparison to MQMAS, The different advantages of DAS and MQMAS make them useful complementary techniques in many cases,Two additional methods are also presented for extracting the chemical shift anisotropy (CSA) directly for quadrupolar nuclei using the multiple-quantum scheme, (C) 1997 Elsevier Science B,V.

%B Solid State Nuclear Magnetic Resonance %V 8 %P 1-16 %8 Mar %@ 0926-2040 %G English %U ://WOS:A1997WY62900001 %N 1 %M WOS:A1997WY62900001 %! Multiple-quantum magic-angle spinning and dynamic-angle spinning NMR spectroscopy of quadrupolar nuclei %R Doi 10.1016/S0926-2040(96)01277-5 %0 Journal Article %J Journal of the American Chemical Society %D 1996 %T Triple-quantum two-dimensional Al-27 magic-angle spinning nuclear magnetic resonance spectroscopic study of aluminosilicate and aluminate crystals and glasses %A Baltisberger, J. H. %A Xu, Z. %A Stebbins, J. F. %A Wang, S. H. %A Pines, A. %K anorthite %X

A new two-dimensional magic-angle spinning NMR experiment(1,2) using multiple-quantum coherences of half-integer quadrupolar nuclei was used to study Al-27 sites in crystalline samples of leucite (KAlSi2O6), anorthite (CaAl2Si2O8), and kyanite (Al2SiO5), as well as CaAl2Si2O8 glass and a magnesium aluminoborate glass. In the crystals, multiple sites are partially resolved and new results for isotropic chemical shifts and quadrupolar parameters are derived, using data collected at a single magnetic field. Data for both leucite and anorthite are consistent with previous results that correlate chemical shifts with mean intertetrahedral bond angle. Signal can be obtained from sites with quadrupolar coupling constants as large as 9 MHz, but intensities are reduced. In the aluminoborate glass, peaks for sites with different Al coordination numbers are well separated. The lack of such features in CaAl2Si2O8 glass rules out the presence of significant quantities of AlO5 and AlO6 groups.

%B Journal of the American Chemical Society %V 118 %P 7209-7214 %8 Jul 31 %@ 0002-7863 %G English %U ://WOS:A1996VA02600027 %N 30 %M WOS:A1996VA02600027 %! Triple-quantum two-dimensional Al-27 magic-angle spinning nuclear magnetic resonance spectroscopic study of aluminosilicate and aluminate crystals and glasses %R Doi 10.1021/Ja9606586 %0 Journal Article %J Journal of Physical Chemistry %D 1995 %T Solid-State O-17 Magic-Angle and Dynamic-Angle Spinning Nmr-Study of the Sio2 Polymorph Coesite %A Grandinetti, P. J. %A Baltisberger, J. H. %A Farnan, I. %A Stebbins, J. F. %A Werner, U. %A Pines, A. %K oxygen %X

Five distinctly resolved O-17 solid-state NMR resonances in room temperature coesite, an SiO2 polymorph, have been observed and assigned using dynamic-angle spinning (DAS) at 11.7 T along with magic-angle spinning (MAS) spectra at 9.4 and 11.7 T. The O-17 quadrupolar parameters for each of the five oxygen environments in coesite are correlated with the Si-O-Si bridging bond angles determined by diffraction experiments. The sign of e(2)qQ/h along with the orientation of the electric field gradient for oxygen in the Si-O-Si linkage were determined from a Townes-Dailey analysis of the data.

%B Journal of Physical Chemistry %V 99 %P 12341-12348 %8 Aug 10 %@ 0022-3654 %G English %U ://WOS:A1995RN70600045 %N 32 %M WOS:A1995RN70600045 %! Solid-State O-17 Magic-Angle and Dynamic-Angle Spinning Nmr-Study of the Sio2 Polymorph Coesite %R Doi 10.1021/J100032a045 %0 Journal Article %J Nature %D 1992 %T Quantification of the Disorder in Network-Modified Silicate-Glasses %A Farnan, I. %A Grandinetti, P. J. %A Baltisberger, J. H. %A Stebbins, J. F. %A Werner, U. %A Eastman, M. A. %A Pines, A. %K time %X

Local order in silicate glasses has been observed by many experimental techniques to be similar to that in crystalline materials. Details of the intermediate-range order are more elusive, but essential for understanding the lack of long-range symmetry in glasses and the effect of composition on glass structure. Two-dimensional O-17 dynamic-angle-spinning nuclear magnetic resonance experiments reveal intermediate-range order in the distribution of inter-tetrahedral (Si-O-Si) bond angles and a high degree of order in the disposition of oxygen atoms around the network-modifying cations.

%B Nature %V 358 %P 31-35 %8 Jul 2 %@ 0028-0836 %G English %U ://WOS:A1992JB34100043 %N 6381 %M WOS:A1992JB34100043 %! Quantification of the Disorder in Network-Modified Silicate-Glasses %R Doi 10.1038/358031a0 %0 Journal Article %J Geochimica Et Cosmochimica Acta %D 1988 %T Diffusive Motion in Alkali Silicate Melts - an Nmr-Study at High-Temperature %A Liu, S. B. %A Stebbins, J. F. %A Schneider, E. %A Pines, A. %B Geochimica Et Cosmochimica Acta %V 52 %P 527-538 %8 Feb %@ 0016-7037 %G English %U ://WOS:A1988M310000028 %N 2 %M WOS:A1988M310000028 %! Diffusive Motion in Alkali Silicate Melts - an Nmr-Study at High-Temperature %R Doi 10.1016/0016-7037(88)90108-1 %0 Journal Article %J Physics and Chemistry of Minerals %D 1988 %T A Si-29 Nuclear Magnetic-Resonance Study of Silicon-Aluminum Ordering in Leucite and Analcite %A Murdoch, J. B. %A Stebbins, J. F. %A Carmichael, I. S. E. %A Pines, A. %B Physics and Chemistry of Minerals %V 15 %P 370-382 %@ 0342-1791 %G English %U ://WOS:A1988M683200009 %N 4 %M WOS:A1988M683200009 %! A Si-29 Nuclear Magnetic-Resonance Study of Silicon-Aluminum Ordering in Leucite and Analcite %R Doi 10.1007/Bf00311042 %0 Journal Article %J Physics and Chemistry of Minerals %D 1987 %T Relaxation Mechanisms and Effects of Motion in Albite (Naalsi3o8) Liquid and Glass - a High-Temperature Nmr-Study %A Liu, S. B. %A Pines, A. %A Brandriss, M. %A Stebbins, J. F. %B Physics and Chemistry of Minerals %V 15 %P 155-162 %@ 0342-1791 %G English %U ://WOS:A1987L016700007 %N 2 %M WOS:A1987L016700007 %! Relaxation Mechanisms and Effects of Motion in Albite (Naalsi3o8) Liquid and Glass - a High-Temperature Nmr-Study %R Doi 10.1007/Bf00308778 %0 Journal Article %J Journal of Non-Crystalline Solids %D 1987 %T Speciation and Local-Structure in Alkali and Alkaline-Earth Silicate-Glasses - Constraints from Si-29 Nmr-Spectroscopy %A Schneider, E. %A Stebbins, J. F. %A Pines, A. %B Journal of Non-Crystalline Solids %V 89 %P 371-383 %8 Mar %@ 0022-3093 %G English %U ://WOS:A1987G515500011 %N 3 %M WOS:A1987G515500011 %! Speciation and Local-Structure in Alkali and Alkaline-Earth Silicate-Glasses - Constraints from Si-29 Nmr-Spectroscopy %R Doi 10.1016/S0022-3093(87)80279-X %0 Journal Article %J Physics and Chemistry of Minerals %D 1986 %T Defects and Short-Range Order in Nepheline Group Minerals - a Si-29 Nuclear-Magnetic-Resonance Study %A Stebbins, J. F. %A Murdoch, J. B. %A Carmichael, I. S. E. %A Pines, A. %B Physics and Chemistry of Minerals %V 13 %P 371-381 %@ 0342-1791 %G English %U ://WOS:A1986E631100003 %N 6 %M WOS:A1986E631100003 %! Defects and Short-Range Order in Nepheline Group Minerals - a Si-29 Nuclear-Magnetic-Resonance Study %0 Journal Article %J Review of Scientific Instruments %D 1986 %T New Probe for High-Temperature Nmr-Spectroscopy with Ppm Resolution %A Stebbins, J. F. %A Schneider, E. %A Murdoch, J. B. %A Pines, A. %A Carmichael, I. S. E. %B Review of Scientific Instruments %V 57 %P 39-42 %8 Jan %@ 0034-6748 %G English %U ://WOS:A1986AXA2000010 %N 1 %M WOS:A1986AXA2000010 %! New Probe for High-Temperature Nmr-Spectroscopy with Ppm Resolution %R Doi 10.1063/1.1139115 %0 Journal Article %J Nature %D 1985 %T A High-Temperature High-Resolution Nmr-Study of Na-23, Al-27 and Si-29 in Molten Silicates %A Stebbins, J. F. %A Murdoch, J. B. %A Schneider, E. %A Carmichael, I. S. E. %A Pines, A. %B Nature %V 314 %P 250-252 %@ 0028-0836 %G English %U ://WOS:A1985ADT9900039 %N 6008 %M WOS:A1985ADT9900039 %! A High-Temperature High-Resolution Nmr-Study of Na-23, Al-27 and Si-29 in Molten Silicates %R Doi 10.1038/314250a0