Application of rotor-synchronized amplitude-modulated cross-polarization in a 13C-1H spin pair under fast magic-angle spinning
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.
UMR 7510 CNRS, Universite Louis Pasteur, Strasbourg Cedex, 67008, France.
J
Raya
J
Hirschinger