Rotor-synchronized acquisition of quadrupolar satellite-transition NMR spectra: practical aspects and double-quantum filtration

Ashbrook, S.E. and Wimperis, S. (2005) Rotor-synchronized acquisition of quadrupolar satellite-transition NMR spectra: practical aspects and double-quantum filtration. Journal of Magnetic Resonance, 177(1), pp. 44-55. (doi: 10.1016/j.jmr.2005.06.013)

Abstract

The very broad resonances of quadrupolar (spin I > 1/2) nuclei are resolved by magic angle spinning (MAS) into a large number of spinning sidebands, each of which often remains anisotropically broadened. The quadrupolar interaction can be removed to a first-order approximation if the MAS NMR spectrum is acquired in a rotor-synchronized fashion, aliasing the spinning sidebands onto a centreband and thereby increasing the signal-to-noise ratio in the resulting, possibly second-order broadened, spectrum. We discuss the practical aspects of this rotor-synchronization in the direct (t2) time domain, demonstrating that the audiofrequency filters in the receiver section of the spectrometer have a significant impact on the precise timings needed in the experiment. We also introduce a novel double-quantum filtered rotor-synchronized experiment for half-integer spin quadrupolar (spin I = 3/2, 5/2, etc.) nuclei that makes use of central-transition-selective inversion pulses to both excite and reconvert double-quantum coherences and yields a simplified spectrum containing only the ST1 (mI = ± 1/2 ↔ ± 3/2) satellite-transition lineshapes. For spin I = 5/2 nuclei, such as 17O and 27Al, this spectrum may exhibit a significant resolution increase over the conventional central-transition spect

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Wimperis, Professor Stephen
• Authors: Ashbrook, S.E., and Wimperis, S.
• Subjects: Q Science > QD Chemistry
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of Magnetic Resonance
• ISSN: 1090-7807
• ISSN (Online): 1096-0856
• Published Online: 11 August 2005