Isotropic Chemical-Shifts and Quadrupolar Parameters for O-17 Using Dynamic-Angle Spinning Nmr

TitleIsotropic Chemical-Shifts and Quadrupolar Parameters for O-17 Using Dynamic-Angle Spinning Nmr
Publication TypeJournal Article
Year of Publication1992
AuthorsMueller K.T, Baltisberger J.H, Wooten E.W, Pines A
JournalJournal of Physical Chemistry
Volume96
Issue17
Pagination7001-7004
Date PublishedAug 20
ISBN Number0022-3654
Accession NumberWOS:A1992JK80700028
Keywordszeolites
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.

URL<Go to ISI>://WOS:A1992JK80700028
DOI10.1021/J100196a028
Short TitleIsotropic Chemical-Shifts and Quadrupolar Parameters for O-17 Using Dynamic-Angle Spinning Nmr
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