Dynamic nuclear polarization at very low magnetic fields.

The recent developments in dynamic nuclear polarization (DNP) at low magnetic fields are presented. The first part of the paper is dedicated to DNP theory for 14N nitroxide systems. It is shown that the lower the magnetic field, the higher the DNP factor. In the second part the material necessary to perform DNP in a low magnetic field is described. The third part is devoted to potential biological applications such as oximetry and free radical imaging.