@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 {487, title = {Nmr-Studies of the Surface-Structure and Dynamics of Semiconductor Nanocrystals}, journal = {Chemical Physics Letters}, volume = {198}, year = {1992}, note = {Chem Phys LettJt385Times Cited:77Cited References Count:27}, month = {Oct 16}, pages = {431-436}, abstract = {

H-1 NMR studies of thiophenol capping groups on cadmium sulfide nanocrystals demonstrate that the coverage of the capping molecule depends on the size of the nanocrystal. Data are presented which show that as the size of the nanocrystal increases, the coverage of thiophenol decreases. In addition, information about the overall tumbling of the nanocrystal and the motion of the capping groups relative to the surface can be obtained from linewidth studies, indicating that the rotation of the capping groups is hindered in the smaller nanocrystals (r almost-equal-to 12 angstrom) and becomes less so in larger nanocrystals (r almost-equal-to 20 angstrom). The coverage data are related to the electronic properties of this important class of compounds.

}, keywords = {relaxation}, isbn = {0009-2614}, doi = {Doi 10.1016/0009-2614(92)80023-5}, url = {://WOS:A1992JT38500001}, author = {Sachleben, J. R. and Wooten, E. W. and Emsley, L. and Pines, A. and Colvin, V. L. and Alivisatos, A. P.} } @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 {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.} }