Efficient double-quantum excitation in rotational resonance NMR.
We present a new technique for double-quantum excitation in magic-angle-spinning solid-state NMR. The method involves (i) preparation of nonequilibrium longitudinal magnetization; (ii) mechanical excitation of zero-quantum coherence by spinning the sample at rotational resonance, and (iii) phase-coherent conversion of the zero-quantum coherence into double-quantum coherence by frequency-selective spin inversion. The double-quantum coherence is converted into observable magnetization by reversing the excitation process, followed by a pi/2 pulse. The method is technically simple, does not require strong RF fields, and is feasible at high spinning frequencies. In [(13)C(2),(15)N]-glycine, with an internuclear (13)C-(13)C distance of 0.153 nm, we achieve a double-quantum filtering efficiency of approximately 56%. In [11, 20-(13)C(2)]-all-E-retinal, with an internuclear (13)C-(13)C distance of 0.296 nm, we obtain approximately 45% double-quantum filtering efficiency.
Karlsson
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T
Division of Physical Chemistry, Stockholm University, Stockholm, S-106 91, Sweden.
Edén
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M
Luthman
H
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Levitt
M H
MH
D002247:Carbon Isotopes; D005998:Glycine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008968:Molecular Conformation; D009584:Nitrogen; D011789:Quantum Theory; D012172:Retinaldehyde / Q000737:chemistry*
D002247:Carbon Isotopes; D009584:Nitrogen; D012172:Retinaldehyde; D005998:Glycine