LOCALIZED CROSS-POLARIZATION IN SOLIDS

Single quantum heteronuclear cross-polarization in solids is strongly sensitive to resonance offsets. In the presence of main field- or radi o-frequency field gradients, the cross-polarization efficiency, theref ore, shows a strong spatial dependence, which represents a new princip le for localized NMR in solids. Since slice-selective excitation is ac hieved simultaneously to cross-polarization, the suggested pulse seque nces avoid the use of shaped pulses, the application of which is probl ematic with solids. The dependence of the localization efficiency on e xperimental and sample parameters is analyzed theoretically far a spin -in system in the presence of a static or a radio-frequency magnetic f ield gradient. The resulting slice profiles and the calculated depende nce of the slice thickness on the parameters of the basic cross-polari zation procedures are discussed and confirmed experimentally on the ex ample of H-1-C-13 Spin systems.