Topical Developments in High-Field Dynamic Nuclear Polarization.

We report our recent efforts directed at improving high-field dynamic nuclear polarization (DNP) expts. We investigated a series of thiourea nitroxide radicals and the assocd. DNP enhancements ranging from $ε$=25 to 82, which demonstrate the impact of mol. structure on performance. We directly polarized low-gamma nuclei, including 13C, 2H, and 17O, by the cross effect mechanism using trityl radicals as a polarization agent. We discuss a variety of sample prepn. techniques for DNP with emphasis on the benefits of methods that do not use a glass-forming cryoprotecting matrix. Lastly, we describe a corrugated waveguide for use in a 700 MHz/460 GHz DNP system that improves microwave delivery and increases enhancements up to 50 %. [on SciFinder(R)]