DEUTERIUM TO CARBON CROSS-POLARIZATION IN LIQUID-CRYSTALS

The theory describing nuclear cross-polarization from a spin-1 to spin -1/2 is generalized to sweeps of the radio-frequency field amplitude. This allows efficient cross-polarization over the entire width of the deuterium NMR spectrum of partially oriented systems, such as liquid c rystals. Such experiments permit the assignment and measurement of the deuterium quadrupolar couplings, and hence the quantification of the order parameters which characterize the dynamics of such systems. The evolution of the spin system can be understood in terms of individual quasiadiabatic population exchanges, allowing the prediction of the ef fects of the various experimental parameters on the efficiency of cros s-polarization. (C) 1998 American Institute of Physics.