Ac. Kolbert et Sl. Gann, VARIABLE-EFFECTIVE-FIELD CROSS-POLARIZATION - AN APPROACH TO BROAD-BAND HARTMANN-HAHN MATCHING IN MAS NMR, Chemical physics letters, 224(1-2), 1994, pp. 86-90
A method for broadening the Hartmann-Hahn matching condition for cross
polarization under magic angle spinning is presented. Variable-effect
ive-field cross polarization (VEFCP) employs different effective radio
-frequency (rf) fields on the H-1 channel during mixing, while the C-1
3 rf field remains constant. VEFCP is shown to result in both a broade
r matching condition, and a more rapid polarization transfer than ordi
nary cross polarization at the Hartmann-Hahn match. Experimental resul
ts on both adamantane and polycarbonate are discussed.