Adiabatic cross-polarization via intermediate dipolar-ordered state
  It is experimentally demonstrated that an adiabatic demagnetization - remagnetization scheme, where the Zeeman order of abundant nuclei is first adiabatically converted into the dipolar order, and then, into the Zeeman order of rare nuclei, can significantly increase polarization of rare nuclei compared to the conventional cross-polarization technique. 
Jae-Seung Lee and A. K. Khitrin