A Combination of Slow and Fast RF Field Modulation for Improved Cross Polarization in Solid-State MAS NMR

A method for efficient Hartmann–Hahn cross polarization under rapid magic-angle sample spinning is presented. It combines rotor-synchronized amplitude modulation of one of the two spin-lock radio-frequency fields for dipolar recoupling, with a slow adiabatic amplitude variation to enhance the net po...

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Bibliographic Details
Published in:Journal of magnetic resonance (1997) 1997-04, Vol.125 (2), p.291-301
Main Authors: Hediger, S., Signer, P., Tomaselli, M., Ernst, R.R., Meier, B.H.
Format: Article
Language:English
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Summary:A method for efficient Hartmann–Hahn cross polarization under rapid magic-angle sample spinning is presented. It combines rotor-synchronized amplitude modulation of one of the two spin-lock radio-frequency fields for dipolar recoupling, with a slow adiabatic amplitude variation to enhance the net polarization transfer. The proposed scheme, called AMAP-CP, allows for cross polarization on the original Hartmann–Hahn matching condition ω1I= ω1S. The polarization transfer is insensitive to chemical-shift offsets, rotation frequency, and inhomogeneity of the radiofrequency field.
ISSN:1090-7807
1096-0856
DOI:10.1006/jmre.1997.1109