Dissolution dynamic nuclear polarization efficiency enhanced by Hartmann–Hahn cross polarization

Dynamic nuclear polarization (DNP) can be used to increase the polarization of nuclei by utilizing the higher electron polarization. Typically, in dissolution DNP heteronuclei are directly polarized due to their longer relaxation times. We present the combination of DNP to protons with subsequent cross polarization to 13C followed by dissolution to solution state. The experiment was implemented using a modified dissolution DNP probe. For a [13C]urea sample doped with TEMPO the carbon polarization and its build-up rate could be increased by a factor of two using CP. With small losses, this gain could be transferred to the solution by dissolution.