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  • Title: Application of rotor-synchronized amplitude-modulated cross-polarization in a 13C-1H spin pair under fast magic-angle spinning.
    Author: Raya J, Hirschinger J.
    Journal: J Magn Reson; 1998 Aug; 133(2):341-51. PubMed ID: 9716477.
    Abstract:
    Rotor-synchronized amplitude-modulated Hartmann-Hahn cross-polarization has been applied under fast magic-angle spinning to a powder sample of ferrocene. The influence on the cross-polarization process of the heteronuclear double quantum (flop-flop) transitions induced by the amplitude modulation for low ratios of the radiofrequency-field strength to the spinning speed is studied in details. The experimental data are in good agreement with theoretical calculations for a two-spin <SGMLEXP TYPE="INLINE">12 system, although the intensity of the double quantum transitions is observed to be significantly smaller than expected. Moreover, it is shown that an efficient polarization transfer at the Hartmann-Hahn centerband matching condition as well as a broadening of the matching conditions is obtained by an appropriate partial scaling of the effective radiofrequency fields which minimizes the destructive effect of double quantum cross-polarization. Copyright 1998 Academic Press.
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