A High-Conversion-Factor, Double-Resonance Structure for High-Field Dynamic Nuclear Polarization |
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Authors: | G Annino J A Villanueva-Garibay P J M van Bentum A A K Klaassen A P M Kentgens |
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Institution: | 1. Istituto per i Processi Chimico-Fisici, CNR, via G. Moruzzi 1, 56124, Pisa, Italy 2. Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 1, 6525 ED, Nijmegen, The Netherlands
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Abstract: | This contribution presents a novel design of a double-resonance structure for high-field dynamic nuclear polarization operating at 95 GHz and 144 MHz, in which a miniaturized radiofrequency coil is integrated within a single-mode nonradiative dielectric resonator. After a detailed discussion of the design principles, the conversion factors of this system are determined by means of microwave and radiofrequency measurements. The obtained results, 1.68 mT/W1/2 for the microwave conversion factor and 0.8 mT/W1/2 for the radiofrequency conversion factor, represent the state-of-the-art among the double-resonance structures. Simultaneous electron paramagnetic resonance and liquid-state 1H nuclear magnetic resonance experiments are performed on samples of nitroxide radical 2,2,6,6-tetramethylpiperidine-1-oxyl dissolved in a mixture of water and dioxane. A maximum dynamic nuclear polarization enhancement of about ?16 is obtained at a microwave power of 70 mW with a radical concentration of 10 mM in nanoliter-sized sample volumes. These results are discussed in view of further improvements and applications of the proposed double-resonance structure. |
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