Adiabatic cross-polarization

Abstract

A scheme of adiabatic cross-polarization is described. It is based on demagnetization - remagnetization, when the Zeeman order of abundant nuclei in the laboratory frame is first adiabatically converted into the dipolar order, and then, into the Zeeman order of rare nuclei. The scheme, implemented with two low-power frequency-sweeping pulses, is very efficient for static samples and can significantly increase polarization of rare nuclei, compared to the conventional Hartmann-Hahn cross-polarization. The experimental examples are presented for solids, liquid crystal, and molecules in a liquid-crystalline solvent.