title: Liquid state DNP using a 260 GHz high power gyrotron.
abstract: Dynamic nuclear polarization (DNP) at high magnetic fields (9.2 T, 400 MHz (1)H NMR frequency) requires high microwave power sources to achieve saturation of the EPR transitions. Here we describe the first high-field liquid-state DNP results using a high-power gyrotron microwave source (20 W at 260 GHz). A DNP enhancement of -29 on water protons was obtained for an aqueous solution of Fremy's Salt; in comparison the previous highest value was -10 using a solid-state microwave power source (maximum power 45 mW). The increased enhancements are partly due to larger microwave saturation and elevated sample temperature. These experimentally observed DNP enhancements, which by far exceed the predicted values extrapolated from low-field DNP experiments, demonstrate experimentally that DNP is possible in the liquid state also at high magnetic fields.
authors.affiliation: Institute of Physical and Theoretical Chemistry and Center of Biomolecular Magnetic Resonance, Goethe University Frankfurt, Germany.
authors.forename: Vasyl
authors.initials: V
authors.lastname: Denysenkov
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Prandolini
authors.forename: Marat
authors.initials: M
authors.lastname: Gafurov
authors.forename: Deniz
authors.initials: D
authors.lastname: Sezer
authors.forename: Burkhard
authors.initials: B
authors.lastname: Endeward
authors.forename: Thomas F
authors.initials: TF
authors.lastname: Prisner
mesh_terms: D009682:Magnetic Resonance Spectroscopy / Q000295:instrumentation* / Q000379:methods; D008872:Microwaves; D056004:Molecular Dynamics Simulation; D009603:Nitroso Compounds / Q000737:chemistry
chemical_list: D009603:Nitroso Compounds; C001259:Fremy's salt