A spectrometer for EPR,DNP, and multinuclear high-resolution NMR |
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| Institution: | 1. Department of Chemistry, Langelandsgade 140, Aarhus University, Aarhus C DK-8000, Denmark;2. Laboratory of Inorganic Chemistry, Department of Chemistry and Applied Biosciences, ETH Zurich, Zürich CH-8093, Switzerland;1. Fakultät Physik, Technische Universität Dortmund, 44221 Dortmund, Germany;2. Department of Physics, University of Guelph, Guelph, Ontario N1G 2W1, Canada;1. School of Health Sciences, University of East Anglia, Norwich NR4 7TJ, UK;2. Department of Earth and Environment Sciences, University of Alicante. 03690 Alicante, Spain;1. School of Civil Engineering, Dalian University of Technology, Dalian 116024, China;2. College of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, China;3. State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454003, China;1. Department of Physics, University of Warwick, Coventry CV4 7AL, UK;2. Department of Chemistry, Brandeis University, Waltham, MA 02454-9110, USA;3. Francis Bitter Magnet Laboratory, Massachusetts Institute of Technology, 150 Albany Street Cambridge, MA 02139, USA |
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| Abstract: | We describe a magnetic resonance spectrometer capable of EPR, dynamic nuclear polarization, and multinuclear high-resolution NMR. The operating field is 1.4 T, corresponding to Larmor frequencies of 40 GHz and 60 MHz for electrons and protons, respectively. The microwave side of the probe is based on a Fabry-Perot resonator (FPR ), an open structure that enhances power-to-field conversion for efficient saturation of the EPR for dynamic polarization, and further permits in situ detection for EPR. This allows the external field to be set at, rather than scanned for, the optimal DNP position. Moreover, we have found that adjustments necessary for maximizing DNP may be done via optimization of the EPR signal, a feature of particular significance for samples which exhibit NMR signals on the borderline of detectability, i.e., samples for which DNP is of special importance. 'H and '3C polarization enhancements achieved using the FPR are compared with devices used by others, in particular the horn /reflector system used by Wind and co-workers. Direct '3C enhancements large enough to detect 2.5 x 10'6 spins in (fluoranthenyl)2 PF6 after a single one-second polarization period have been obtained, and the first high-field 'Li DNP results are also presented. |
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