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Resolution Enhancement in Multiple-Quantum MAS NMR Spectroscopy

✍ Scribed by Ingo Schnell; Adonis Lupulescu; Siegfried Hafner; Dan E. Demco; Hans W. Spiess

Publisher: Elsevier Science
Year: 1998
Tongue: English
Weight: 287 KB
Volume: 133
Category: Article
ISSN: 1090-7807
DOI: 10.1006/jmre.1998.1432

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✦ Synopsis

Two techniques for resolution and sensitivity enhancement are introduced in multiple-quantum (MQ) MAS spectroscopy of rigid solids. The first makes use of ultrafast MAS with spinning frequencies of up to 35 kHz, while the second combines MAS at moderately fast spinning frequencies of about 13 kHz with multiple-pulse (MP) dipolar decoupling. For the latter approach, a semiwindowless WHH-4 sequence is applied during the MQ evolution period (MQ dimension) and/or detection period (singlequantum dimension). In the MQ dimension, the MP sequence has to be supplemented by two bracketing pulses in order to preserve the order and the intensities of the evolving MQ coherences. Double-quantum 1 H NMR spectra of L-alanine recorded using both decoupling techniques are shown and compared to each other. Triple-quantum 1 H NMR spectra under ultrafast MAS conditions are also presented.

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