{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/77351"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/77351","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Dynamics of Dissociative Chemisorption: Methane on Tungsten Single Crystal Surfaces","abstract":"Chemisorption of simple molecular gases on clean metal surfaces is usually rapid, with vanishingly small activation energies and large sticking coefficients. However, for more complicated molecules, such as saturated hydrocarbons, chemisorption is often a slow process which involves thermal excitation over relatively high barriers. We have studied one such system: the dissociation of methane on clean tungsten single crystal surfaces. The purpose of this study is to explore the nature of the elementary excitations which bring about dissociation and subsequent adsorption. Our effort has been concentrated upon studying the effect of thermal excitations of the gas as well as the importance of the crystal structure of the metal surface.","abstract_html":"Chemisorption of simple molecular gases on clean metal surfaces is usually rapid, with vanishingly small activation energies and large sticking coefficients. However, for more complicated molecules, such as saturated hydrocarbons, chemisorption is often a slow process which involves thermal excitation over relatively high barriers. We have studied one such system: the dissociation of methane on clean tungsten single crystal surfaces. The purpose of this study is to explore the nature of the elementary excitations which bring about dissociation and subsequent adsorption. Our effort has been concentrated upon studying the effect of thermal excitations of the gas as well as the importance of the crystal structure of the metal surface.","abstract_has_math":false,"creators":["Lo, Tai-Chin"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2015,"date_issued":"2015-05-13T15:41:36Z","date_published":"2015-05-13T15:41:36Z","updated_at":"2026-07-22T22:26:10Z","subjects":["Physics, Molecular"],"languages":["eng"],"rights":[],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["(UMI)AAI8309976"],"render_values":[{"text":"(UMI)AAI8309976","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/77351","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Lo, Tai-Chin"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2015-05-13T15:41:36Z","10000-01-01","1983"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Physics"]},{"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":["Physics, Molecular"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["eng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/77351","(UMI)AAI8309976"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Chemisorption of simple molecular gases on clean metal surfaces is usually rapid, with vanishingly small activation energies and large sticking coefficients. However, for more complicated molecules, such as saturated hydrocarbons, chemisorption is often a slow process which involves thermal excitation over relatively high barriers. We have studied one such system: the dissociation of methane on clean tungsten single crystal surfaces. The purpose of this study is to explore the nature of the elementary excitations which bring about dissociation and subsequent adsorption. Our effort has been concentrated upon studying the effect of thermal excitations of the gas as well as the importance of the crystal structure of the metal surface.","We have performed molecular beam studies on the (100), (211), (111), (411), and (811) planes of tungsten, using a Kelvin vibrating capacitor for contact potential measurements. It has been found that excitation of the gas alone is sufficient to bring about reaction with the tungsten surfaces. The barriers to dissociation of methane are sensitive to the atomic arrangements on the crystal surface. The empirical activation barrier of methane on W(100), the most unreactive crystal plane, is (TURN) 9.7 kcal/mole. This is about 30% higher than the empirical activation barrier of methane on W(211), which is (TURN) 7.5 kcal/mole.","The results are well described by a model invoking molecular adsorption of the methane molecule, followed by dissociation of those molecules which have sufficient vibrational energies of higher bending modes, in order to extend the H-H distance to a critical length beyond the equilibrium value.","Made available in DSpace on 2015-05-13T15:41:36Z (GMT). No. of bitstreams: 2 license.txt: 4848 bytes, checksum: 96035ab3f5e1c23cc7138a224ce498bd (MD5) 8309976.PDF: 4433872 bytes, checksum: 6000f56222a2210857ea2a6dcb9aa531 (MD5) Previous issue date: 1983","Embargo set by: Seth Robbins for item 78562 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","142 p.","Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1983."]},{"key":"dc:title","label":"Title","values":["Dynamics of Dissociative Chemisorption: Methane on Tungsten Single Crystal Surfaces"]}]}],"canonical_facts":{"dc:creator":["Lo, Tai-Chin"],"dc:date":["2015-05-13T15:41:36Z","10000-01-01","1983"],"dc:description":["Chemisorption of simple molecular gases on clean metal surfaces is usually rapid, with vanishingly small activation energies and large sticking coefficients. However, for more complicated molecules, such as saturated hydrocarbons, chemisorption is often a slow process which involves thermal excitation over relatively high barriers. We have studied one such system: the dissociation of methane on clean tungsten single crystal surfaces. The purpose of this study is to explore the nature of the elementary excitations which bring about dissociation and subsequent adsorption. Our effort has been concentrated upon studying the effect of thermal excitations of the gas as well as the importance of the crystal structure of the metal surface.","We have performed molecular beam studies on the (100), (211), (111), (411), and (811) planes of tungsten, using a Kelvin vibrating capacitor for contact potential measurements. It has been found that excitation of the gas alone is sufficient to bring about reaction with the tungsten surfaces. The barriers to dissociation of methane are sensitive to the atomic arrangements on the crystal surface. The empirical activation barrier of methane on W(100), the most unreactive crystal plane, is (TURN) 9.7 kcal/mole. This is about 30% higher than the empirical activation barrier of methane on W(211), which is (TURN) 7.5 kcal/mole.","The results are well described by a model invoking molecular adsorption of the methane molecule, followed by dissociation of those molecules which have sufficient vibrational energies of higher bending modes, in order to extend the H-H distance to a critical length beyond the equilibrium value.","Made available in DSpace on 2015-05-13T15:41:36Z (GMT). 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