High-resolution solid-state NMR of quadrupolar nuclei
| Autor: | Michael D. Meadows, Eric Oldfield, Karen Ann Smith, Robert Skarjune, T. Michael Rothgeb, Robert A. Kinsey |
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| Rok vydání: | 1982 |
| Předmět: | |
| Zdroj: | Proceedings of the National Academy of Sciences. 79:1351-1355 |
| ISSN: | 1091-6490 0027-8424 |
| DOI: | 10.1073/pnas.79.4.1351 |
| Popis: | We report the observation of high-resolution solid-state NMR spectra of 23 Na ( I = [unk]), 27 Al ( I = [unk]) and 51 V ( I = [unk]) in various inorganic systems. We show that, contrary to popular belief, relatively high-resolution (≈10 ppm linewidth) spectra may be obtained from quadrupolar systems, in which electric quadrupole coupling constants ( e 2 qQ/h ) are in the range ≈1-5 MHz, by means of observation of the (½, -½) spin transition. The (½, -½) transition for all nonintegral spin quadrupolar nuclei ( I = [unk], [unk], [unk], or [unk]) is only normally broadened by dipolar, chemical shift (or Knight shift) anisotropy or second-order quadrupolar effects, all of which are to a greater or lesser extent averaged under fast magic-angle sample rotation. In the case of 23 Na and 27 Al, high-resolution spectra of 23 NaNO 3 ( e 2 qQ/h ≈300 kHz) and α- 27 Al 2 O 3 ( e 2 qQ/h ≈2-3 MHz) are presented; in the case of 51 V 2 O 5 ( e 2 qQ/h ≈800 kHz), rotational echo decays are observed due to the presence of a ≈10 3 -ppm chemical shift anisotropy. The observation of high-resolution solid-state spectra of systems having spins I = [unk], [unk], and [unk] in asymmetric environments opens up the possibility of examining about two out of three nuclei by solid-state NMR that were previously thought of as “inaccessible” due to the presence of large (a few megahertz) quadrupole coupling constants. Preliminary results for an I = [unk] system, 93 Nb, having e 2 qQ/h ≈19.5 MHz, are also reported. |
| Databáze: | OpenAIRE |
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