@article {492, title = {Isotropic Chemical-Shifts and Quadrupolar Parameters for O-17 Using Dynamic-Angle Spinning Nmr}, journal = {Journal of Physical Chemistry}, volume = {96}, year = {1992}, note = {J Phys Chem-UsJk807Times Cited:66Cited References Count:48}, month = {Aug 20}, pages = {7001-7004}, abstract = {

Several oxygen-17-enriched silicates were studied using dynamic-angle spinning (DAS) NMR spectroscopy at two magnetic field strengths. The DAS method averages second-order quadrupolar interactions by reorienting a sample about a time-dependent axis, thereby yielding high-resolution spectra for half-odd integer spin quadrupolar nuclei such as oxygen-17. A narrow spectral line is observed for each distinct oxygen site in a powdered sample at the sum of the isotropic chemical shift and the field-dependent isotropic second-order quadrupolar shift. Using equations for the total shift observed at two field strengths, the chemical shift is uniquely determined together with a product of the quadrupolar coupling constant (C(Q) = e2qQ/h) and the quadrupolar asymmetry parameter (eta). For one silicate, we demonstrate aa computer program that uses the isotropic shifts and quadrupolar products as constraints and provides simulations of overlapped magic-angle spinning line shapes. In this way the quadrupolar parameters, C(Q) and eta, are determined separately for each crystallographic site. The silicates studied include the discrete orthosilicates larnite (Ca2SiO4) and forsterite (Mg2SiO4), as well as diopside (CaMgSi2O6), wollastonite (CaSiO3), and clinoenstatite (MgSiO3), which are minerals composed of chains of silicon-oxygen tetrahedra.

}, keywords = {zeolites}, isbn = {0022-3654}, doi = {Doi 10.1021/J100196a028}, url = {://WOS:A1992JK80700028}, author = {Mueller, K. T. and Baltisberger, J. H. and Wooten, E. W. and Pines, A.} } @article {484, title = {New Angles in Nuclear-Magnetic-Resonance Sample Spinning}, journal = {Accounts of Chemical Research}, volume = {25}, year = {1992}, note = {Accounts Chem ResHu248Times Cited:41Cited References Count:29}, month = {May}, pages = {209-215}, keywords = {axis}, isbn = {0001-4842}, doi = {Doi 10.1021/Ar00017a001}, url = {://WOS:A1992HU24800001}, author = {Wooten, E. W. and Mueller, K. T. and Pines, A.} } @article {500, title = {Rb-87 Dynamic-Angle Spinning Nmr-Spectroscopy of Inorganic Rubidium Salts}, journal = {Journal of the American Chemical Society}, volume = {114}, year = {1992}, note = {J Am Chem SocJm979Times Cited:39Cited References Count:28}, month = {Sep 9}, pages = {7489-7493}, abstract = {

Five inorganic rubidium salts, RbCl, RbClO4, Rb2SO4, Rb2CrO4, and RbNO3, were examined using Rb-87 NMR spectroscopy. Significant line narrowing occurs under dynamic-angle spinning (DAS) compared to magic-angle spinning (MAS) or variable-angle spinning (VAS). From DAS spectra acquired at various magnetic field strengths, isotropic chemical shifts and isotropic second-order quadrupolar shifts were obtained. By simulations of single-site line shapes obtained from MAS-detected DAS experiments, complete chemical shift and quadrupolar parameters were determined for each of the three crystallographically distinct rubidium sites in RbNO3.

}, keywords = {cesium}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00045a023}, url = {://WOS:A1992JM97900023}, author = {Baltisberger, J. H. and Gann, S. L. and Wooten, E. W. and Chang, T. H. and Mueller, K. T. and Pines, A.} } @article {504, title = {High-Resolution O-17 Nmr of Solid Silicates}, journal = {Journal of the American Chemical Society}, volume = {113}, year = {1991}, note = {J Am Chem SocEr082Times Cited:90Cited References Count:39}, month = {Jan 2}, pages = {32-38}, abstract = {

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).

}, keywords = {spectra}, isbn = {0002-7863}, doi = {Doi 10.1021/Ja00001a006}, url = {://WOS:A1991ER08200006}, author = {Mueller, K. T. and Wu, Y. and Chmelka, B. F. and Stebbins, J. and Pines, A.} } @article {506, title = {Nmr Probe for Dynamic-Angle Spinning}, journal = {Review of Scientific Instruments}, volume = {62}, year = {1991}, note = {Rev Sci InstrumFp312Times Cited:31Cited References Count:35}, month = {Jun}, pages = {1445-1452}, abstract = {

We describe the design of a probe for dynamic-angle spinning (DAS) NMR experiments, comprised of a spinning cylindrical sample holder whose axis may be reoriented rapidly between discrete directions within the bore of a superconducting magnet. This allows the refocusing of nuclear spin magnetization that evolves under anisotropic interactions such as chemical shift anisotropy and quadrupolar coupling, providing high resolution NMR spectra for quadrupolar nuclei in solid materials. The probe includes an axial air delivery system to bearing and drive jets which support and spin a rotor containing the sample. Axis reorientation is accomplished with a pulley attached to the probehead and coupled to a stepping motor outside of the magnet. The choice of motor and gear ratio is based on an analysis of the moments of inertia of the motor and load, the desired angular resolution, and simplicity of design. Control of angular accuracy and precision are discussed, as well as the efficiency of radiofrequency irradiation and detection. High resolution DAS spectra of oxygen-17 and aluminum-27 nuclei in polycrystalline minerals illustrate the experimental capabilities.

}, keywords = {minerals}, isbn = {0034-6748}, doi = {Doi 10.1063/1.1142465}, url = {://WOS:A1991FP31200011}, author = {Mueller, K. T. and Chingas, G. C. and Pines, A.} } @article {505, title = {Pure-Absorption-Phase Dynamic-Angle Spinning}, journal = {Journal of Magnetic Resonance}, volume = {92}, year = {1991}, note = {J Magn ResonFj100Times Cited:30Cited References Count:15}, month = {May}, pages = {620-627}, keywords = {nuclei}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(91)90359-2}, url = {://WOS:A1991FJ10000018}, author = {Mueller, K. T. and Wooten, E. W. and Pines, A.} } @article {521, title = {Dynamic-Angle Spinning of Quadrupolar Nuclei}, journal = {Journal of Magnetic Resonance}, volume = {86}, year = {1990}, note = {J Magn ResonCu525Times Cited:288Cited References Count:32}, month = {Feb 15}, pages = {470-487}, isbn = {0022-2364}, doi = {Doi 10.1016/0022-2364(90)90025-5}, url = {://WOS:A1990CU52500003}, author = {Mueller, K. T. and Sun, B. Q. and Chingas, G. C. and Zwanziger, J. W. and Terao, T. and Pines, A.} } @article {552, title = {Frequency Selective Nmr Pulse Sequences Generated by Iterative Schemes with Multiple Fixed-Points}, journal = {Molecular Physics}, volume = {67}, year = {1989}, note = {Mol PhysAf151Times Cited:3Cited References Count:24}, month = {Jun 20}, pages = {505-516}, isbn = {0026-8976}, doi = {Doi 10.1080/00268978900101251}, url = {://WOS:A1989AF15100003}, author = {Cho, H. and Mueller, K. T. and Shaka, A. J. and Pines, A.} } @article {554, title = {O-17 Nmr in Solids by Dynamic-Angle Spinning and Double Rotation}, journal = {Nature}, volume = {339}, year = {1989}, note = {NatureU4451Times Cited:177Cited References Count:15}, month = {May 4}, pages = {42-43}, isbn = {0028-0836}, doi = {Doi 10.1038/339042a0}, url = {://WOS:A1989U445100054}, author = {Chmelka, B. F. and Mueller, K. T. and Pines, A. and Stebbins, J. and Wu, Y. and Zwanziger, J. W.} } @article {560, title = {Study of the Aharonov-Anandan Quantum Phase by Nmr Interferometry}, journal = {Physical Review Letters}, volume = {60}, year = {1988}, note = {Phys Rev LettM6160Times Cited:184Cited References Count:43}, month = {Mar 28}, pages = {1218-1220}, isbn = {0031-9007}, doi = {Doi 10.1103/Physrevlett.60.1218}, url = {://WOS:A1988M616000003}, author = {Suter, D. and Mueller, K. T. and Pines, A.} }