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oai:dspace.mit.edu:1721.1/1578302024-12-12T03:59:11Zcom_1721.1_7582com_1721.1_7581col_1721.1_131022

Griffin, Robert G. Mardini, Michael Massachusetts Institute of Technology. Department of Chemistry 2024-12-11T15:05:01Z 2024-12-11T15:05:01Z 2024-02 2024-12-09T18:07:54.312Z https://hdl.handle.net/1721.1/157830 In thirty years of active development, dynamic nuclear polarization (DNP) has emerged as a forefront technique for expanding the scope of solid state nuclear magnetic resonance. For the most part, and particularly at high fields, these advances have come with continuous-wave microwave irradiation and the introduction of nitroxide-based biradicals exploiting the cross effect mechanism. In this thesis, I argue that this approach is not necessarily optimal and report progress towards arbitrary-waveform DNP, in the construction of a suitable solid-state microwave source, and the use of narrow-line monoradicals exploiting the Overhauser effect. My colleagues and I have also investigated the Overhauser mechanism through selective deuteration of radicals, leading to a relatively simple modification which yielded a significant increase in Overhauser enhancement. Finally, I detail studies of two unexplored DNP mechanisms in trityl: the three-spin solid effect and resonant mixing. With solid-state microwave sources and Overhauser radicals, DNP is now more accessible as we can achieve reasonable enhancement without the need for a gyrotron. Moreover, as amplifier and resonator technologies continue to develop, it is likely that pulsed DNP will emerge at high fields and overtake continuous-wave DNP in absolute sensitivity enhancement as well. Ph.D. Massachusetts Institute of Technology Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Copyright retained by author(s) https://creativecommons.org/licenses/by-nc-nd/4.0/ High field dynamic nuclear polarization methods: Microwave sources and mechanisms Thesis application/pdf Doctoral Doctor of Philosophy Publication unknown unknown <Publication xmlns="https://www.openaire.eu/cerif-profile/1.1/" id="2620904b-f6b9-435a-a265-25dae040f776"> <Type xmlns="https://www.openaire.eu/cerif-profile/vocab/COAR_Publication_Types">http://purl.org/coar/resource_type/c_1843</Type> <Title>High field dynamic nuclear polarization methods: Microwave sources and mechanisms</Title> <PublishedIn> <Publication> </Publication> </PublishedIn> <PublicationDate>2024-02</PublicationDate> <Authors> <Author> <DisplayName>Mardini, Michael</DisplayName> <Affiliation> <OrgUnit> </OrgUnit> </Affiliation> </Author> </Authors> <Editors> </Editors> <Publishers> <Publisher> <DisplayName>Massachusetts Institute of Technology</DisplayName> <OrgUnit /> </Publisher> </Publishers> <License>https://creativecommons.org/licenses/by-nc-nd/4.0/</License> <Abstract>In thirty years of active development, dynamic nuclear polarization (DNP) has emerged as a forefront technique for expanding the scope of solid state nuclear magnetic resonance. For the most part, and particularly at high fields, these advances have come with continuous-wave microwave irradiation and the introduction of nitroxide-based biradicals exploiting the cross effect mechanism. In this thesis, I argue that this approach is not necessarily optimal and report progress towards arbitrary-waveform DNP, in the construction of a suitable solid-state microwave source, and the use of narrow-line monoradicals exploiting the Overhauser effect. My colleagues and I have also investigated the Overhauser mechanism through selective deuteration of radicals, leading to a relatively simple modification which yielded a significant increase in Overhauser enhancement. Finally, I detail studies of two unexplored DNP mechanisms in trityl: the three-spin solid effect and resonant mixing. With solid-state microwave sources and Overhauser radicals, DNP is now more accessible as we can achieve reasonable enhancement without the need for a gyrotron. Moreover, as amplifier and resonator technologies continue to develop, it is likely that pulsed DNP will emerge at high fields and overtake continuous-wave DNP in absolute sensitivity enhancement as well.</Abstract> <Access xmlns="http://purl.org/coar/access_right" > </Access> </Publication>