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Separation of isotropic chemical and second-order quadrupolar shifts by multiple-quantum double rotation NMR

Research output: Contribution to Journal/MagazineJournal articlepeer-review

Published
  • Ivan Hung
  • Alan Wong
  • Andy P. Howes
  • Tiit Anupõld
  • Ago Samoson
  • Mark E. Smith
  • D. Holland
  • Steven P. Brown
  • Ray Dupree
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<mark>Journal publication date</mark>1/04/2009
<mark>Journal</mark>Journal of Magnetic Resonance
Issue number2
Volume197
Number of pages8
Pages (from-to)229-236
Publication StatusPublished
<mark>Original language</mark>English

Abstract

Using a two-dimensional multiple-quantum (MQ) double rotation (DOR) experiment the contributions of the chemical shift and quadrupolar interaction to isotropic resonance shifts can be completely separated. Spectra were acquired using a three-pulse triple-quanturn z-filtered pulse sequence and Subsequently sheared along both the nu(1) and nu(2) dimensions. The application of this method is demonstrated for both crystalline (RbNO3) and amorphous samples (vitreous B2O3). The existence of the two rubidium isotopes (Rb-85 and Rb-87) allows comparison of results for two nuclei with different spins (I = 3/2 and 5/2), as well as different dipole and quadrupole moments in a single chemical compound. Being only limited by homogeneous line broadening and sample crystallinity, linewidths of approximately 0.1 and 0.2 ppm can be measured for Rb-87 in the quadrupolar and chemical shift dimensions, enabling highly accurate determination of the isotropic chemical shift and the quadrupolar product, P-Q. For vitreous B2O3, the use of MQDOR allows the chemical shift and electric field gradient distributions to be directly determined-information that is difficult to obtain otherwise due to the presence of second-order quadrupolar broadening. (C) 2009 Elsevier Inc. All rights reserved.