DNP NMR involves the use of paramagnetic agents that possess unpaired electrons, such as stable radicals or metal ions. These agents are introduced into the sample to enhance nuclear polarization. When the sample is irradiated with microwaves at the electron paramagnetic resonance (EPR) frequency, the polarization of the electrons is transferred to the nuclei, significantly increasing the NMR signal. This process is known as the Overhauser effect or the solid effect, depending on the specific mechanism involved.
