{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/72285"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/72285","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Multi-Frequency Electronic Magnetic Resonance Studies of Polycrystalline Systems","abstract":"The conventional electronic magnetic resonance (EMR) spectra of disordered samples often suffer poor resolution due to line-broadening. This thesis describes how a multi-frequency approach applied to the EMR studies of two distinct polycrystalline paramagnetic systems resulted in dramatic resolution improvements.","abstract_html":"The conventional electronic magnetic resonance (EMR) spectra of disordered samples often suffer poor resolution due to line-broadening. This thesis describes how a multi-frequency approach applied to the EMR studies of two distinct polycrystalline paramagnetic systems resulted in dramatic resolution improvements.","abstract_has_math":false,"creators":["Shi, Wenjun"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Chemistry","degree_department":null,"school":null,"contributors":["Belford, R. Linn"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-12-17T21:29:09Z","date_published":"2014-12-17T21:29:09Z","updated_at":"2026-07-22T22:26:06Z","subjects":["Chemistry, Physical"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI9329160"],"render_values":[{"text":"(UMI)AAI9329160","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/72285","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Belford, R. Linn"]},{"key":"dc:creator","label":"Author","values":["Shi, Wenjun"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2014-12-17T21:29:09Z","10000-01-01","1993"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Chemistry"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Chemistry, Physical"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/72285","(UMI)AAI9329160"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["The conventional electronic magnetic resonance (EMR) spectra of disordered samples often suffer poor resolution due to line-broadening. This thesis describes how a multi-frequency approach applied to the EMR studies of two distinct polycrystalline paramagnetic systems resulted in dramatic resolution improvements.","The EMR techniques used include continuous wave electron paramagnetic resonance (cw-EPR) and electron spin echo envelope modulation (ESEEM). Performing the cw-EPR experiments at tenfold higher microwave frequency than the conventional X-band (ca. 9 GHz), greatly improved resolution in the field-dependent electronic Zeeman interaction of the nitro-aromatic radicals adsorbed on metal oxide surfaces. In applying the multi-frequency method to ESEEM to reveal weak superhyperfine (shfs, a) and nuclear quadrupole (NQR) interactions, we have established by model calculations a criterion to identify the "exact cancellation" condition, by which the NQR parameters can be determined directly from the multi-frequency ESEEM spectra. This criterion, taking into account the g and a anisotropies, has been verified by ESEEM experiments performed on the remote nitrogen atom of the meta-dinitrobenzene radical on surfaces. The magnetic parameters obtained this way are in excellent agreement with simulations.","Low-frequency (2-4 GHz) ESEEM spectra of adducts of a copper chelate to an axially coordinated nitrogen-containing Lewis base showed pronounced angle selection patterns. The copper-base systems also provide a large g anisotropy, in which a close approach to cancellation is demonstrated. The nitrogen quadrupole parameters obtained by the pseudo-cancellation method are in reasonably good agreement with those obtained by the orientation-selected ESEEM; the residual discrepancy is discussed.","Low-frequency ESEEM spectra of oxygen-17, magnesium-25, and aluminum-27 in the metal oxides adsorbed with nitro-aromatic species are also reported and discussed.","Made available in DSpace on 2014-12-17T21:29:09Z (GMT). No. of bitstreams: 1 9329160.pdf: 6400885 bytes, checksum: f6596ae9d493b2b4398aa49b688cb345 (MD5) Previous issue date: 1993","Embargo set by: Seth Robbins for item 72453 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","237 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993."]},{"key":"dc:title","label":"Title","values":["Multi-Frequency Electronic Magnetic Resonance Studies of Polycrystalline Systems"]}]}],"canonical_facts":{"dc:contributor":["Belford, R. Linn"],"dc:creator":["Shi, Wenjun"],"dc:date":["2014-12-17T21:29:09Z","10000-01-01","1993"],"dc:description":["The conventional electronic magnetic resonance (EMR) spectra of disordered samples often suffer poor resolution due to line-broadening. This thesis describes how a multi-frequency approach applied to the EMR studies of two distinct polycrystalline paramagnetic systems resulted in dramatic resolution improvements.","The EMR techniques used include continuous wave electron paramagnetic resonance (cw-EPR) and electron spin echo envelope modulation (ESEEM). Performing the cw-EPR experiments at tenfold higher microwave frequency than the conventional X-band (ca. 9 GHz), greatly improved resolution in the field-dependent electronic Zeeman interaction of the nitro-aromatic radicals adsorbed on metal oxide surfaces. In applying the multi-frequency method to ESEEM to reveal weak superhyperfine (shfs, a) and nuclear quadrupole (NQR) interactions, we have established by model calculations a criterion to identify the "exact cancellation" condition, by which the NQR parameters can be determined directly from the multi-frequency ESEEM spectra. This criterion, taking into account the g and a anisotropies, has been verified by ESEEM experiments performed on the remote nitrogen atom of the meta-dinitrobenzene radical on surfaces. The magnetic parameters obtained this way are in excellent agreement with simulations.","Low-frequency (2-4 GHz) ESEEM spectra of adducts of a copper chelate to an axially coordinated nitrogen-containing Lewis base showed pronounced angle selection patterns. The copper-base systems also provide a large g anisotropy, in which a close approach to cancellation is demonstrated. The nitrogen quadrupole parameters obtained by the pseudo-cancellation method are in reasonably good agreement with those obtained by the orientation-selected ESEEM; the residual discrepancy is discussed.","Low-frequency ESEEM spectra of oxygen-17, magnesium-25, and aluminum-27 in the metal oxides adsorbed with nitro-aromatic species are also reported and discussed.","Made available in DSpace on 2014-12-17T21:29:09Z (GMT). No. of bitstreams: 1 9329160.pdf: 6400885 bytes, checksum: f6596ae9d493b2b4398aa49b688cb345 (MD5) Previous issue date: 1993","Embargo set by: Seth Robbins for item 72453 Lift date: Forever Reason: Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","Restricted to the U of I community idenfinitely during batch ingest of legacy ETDs","U of I Only","237 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1993."],"dc:identifier":["http://hdl.handle.net/2142/72285","(UMI)AAI9329160"],"dc:subject":["Chemistry, Physical"],"dc:title":["Multi-Frequency Electronic Magnetic Resonance Studies of Polycrystalline Systems"],"dc:type":["text"],"thesis:degree_discipline":["Chemistry"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:26:06Z"}