Weak Field Dynamic Nuclear Polarization with Phosphorus Radicals.
Dynamic Nuclear Polarization (1) is quite useful for NMR earth field magnetometer (2) whose sensitivity increases with the DNP factor. The interest of free radicals is due to the hyperfine structure which induces an important separation of the electron energy levels at weak fields and increases thereby the DNP factor. The DNP between solvents protons and nitroxide radicals is well known (3). We describe in this paper DNP calculation and measurements on phosphorus radicals which present a more important hyperfine structure.