Ac. Kolbert et A. Bielecki, BROAD-BAND HARTMANN-HAHN MATCHING IN MAGIC-ANGLE-SPINNING NMR VIA AN ADIABATIC FREQUENCY SWEEP, Journal of magnetic resonance. Series A, 116(1), 1995, pp. 29-35
The cross-polarization condition in high-speed magic-angle spinning NM
R is investigated in which the H-1 frequency is swept adiabatically fr
om on-resonance to an off-resonance value during the spin lock, The H-
1 frequency sweep dramatically broadens the matching conditions, leadi
ng to a nearly flat profile over a wide range of C-13 radiofrequency f
ield strengths, These results can be understood by viewing the frequen
cy-swept H-1 spin-locking field in the tilted rotating frame in which
the nutation rate about the effective field, omega(eff) = (omega(1)(2)
+Delta omega(2))(1/2), varies over the duration of the spin lock, broa
dening the matching condition, omega(eff,I) = omega(1S) +/- n omega(r)
. Experimental results on [1-C-13]glycine, [2-C-13,N-15]glycine, and [
3-C-13]D,L-alanine are reported. (C) 1995 Academic Press, Inc.