{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/25549"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/25549","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Giant multipole resonances in lead-208","abstract":"\"The differential photoneutron cross section of 208pb in the energy region 9.9 through 11.2 MeV was measured with gamma energy resolution of approximately 100 KeV using the University of 111inois bremsstrahlung monochromator. Neutrons from a 72% enriched 208pb target and an 88% enriched 206po target were detected with an NE213 scintillation detector having a neutron energy resolution of 11.3 at 4 MeV, a 200 cm flight 'path, and an intrinsic time resolution of 1.6 ns. Neutrons leaving 207pb in its ground state and first two excited states were resolved and angular distributions for these partial cross sections were measured at seven angles from 450 to 1350 inclusive. The total photoabsorption cross section as well as the cross sections for leaving 207pb in its ground st ate and first two excited states were extracted. The data confirm the fine structure seen in earlier photoneutron studies and this structure is found to be mainly electric dipole in character. This assignment is consistent with the results of a recent elastic photon scattering study but inconsistent with an interpretation that ma~es an isovector E2 assignment based on inelastic electron scattering data. The observed integrated g1 strength in the energy region under study is consistent with the amount implied by the tail of a Lorentz line fit to earlier photoneutron data. The present data show local concentrations. and depletions of dipole strength rather than additional strength. The partial cross sections for leaving 207pb in its ground state and first two excited states were analyzed using the statistical compound nucleus model. The data indicate that this model does not correctly describe the branching to the lowest states of 207~b and that the relative amplitudes of the particle-hole states that contribute to the excited states of 208pb are not equal. The 312-hole state is found to dominate the emission process. Only moderate agreement with the observed branching is obtained by allowing for variations among the eight one particle one hole mulitudes that contribute to the decay of 208pb . It is shown that there must be a small g-wave component in the decay to the first excited state of 207 pb . The data, however, cannot be used to determine these amplitudes because there are only three measured cross sections. The experiment can only act as a \"\"necessary\"\" condition for a microscopic description of the excited states of 20Spb in this energy region. Lastly, a calculation of the angular distributions using the Direct-Semi-Direct excitation model and including a broad ( = 2.6 MeV) E2 resonance is not inconsistent with previous suggestions of such a resonance at 10.S MeV.\"","abstract_html":""The differential photoneutron cross section of 208pb in the energy region 9.9 through 11.2 MeV was measured with gamma energy resolution of approximately 100 KeV using the University of 111inois bremsstrahlung monochromator. Neutrons from a 72% enriched 208pb target and an 88% enriched 206po target were detected with an NE213 scintillation detector having a neutron energy resolution of 11.3 at 4 MeV, a 200 cm flight 'path, and an intrinsic time resolution of 1.6 ns. Neutrons leaving 207pb in its ground state and first two excited states were resolved and angular distributions for these partial cross sections were measured at seven angles from 450 to 1350 inclusive. The total photoabsorption cross section as well as the cross sections for leaving 207pb in its ground st ate and first two excited states were extracted. The data confirm the fine structure seen in earlier photoneutron studies and this structure is found to be mainly electric dipole in character. This assignment is consistent with the results of a recent elastic photon scattering study but inconsistent with an interpretation that ma~es an isovector E2 assignment based on inelastic electron scattering data. The observed integrated g1 strength in the energy region under study is consistent with the amount implied by the tail of a Lorentz line fit to earlier photoneutron data. The present data show local concentrations. and depletions of dipole strength rather than additional strength. The partial cross sections for leaving 207pb in its ground state and first two excited states were analyzed using the statistical compound nucleus model. The data indicate that this model does not correctly describe the branching to the lowest states of 207~b and that the relative amplitudes of the particle-hole states that contribute to the excited states of 208pb are not equal. The 312-hole state is found to dominate the emission process. Only moderate agreement with the observed branching is obtained by allowing for variations among the eight one particle one hole mulitudes that contribute to the decay of 208pb . It is shown that there must be a small g-wave component in the decay to the first excited state of 207 pb . The data, however, cannot be used to determine these amplitudes because there are only three measured cross sections. The experiment can only act as a ""necessary"" condition for a microscopic description of the excited states of 20Spb in this energy region. Lastly, a calculation of the angular distributions using the Direct-Semi-Direct excitation model and including a broad ( = 2.6 MeV) E2 resonance is not inconsistent with previous suggestions of such a resonance at 10.S MeV."","abstract_has_math":false,"creators":["Bell, Zane William"],"institution":null,"degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Physics","degree_department":null,"school":null,"contributors":["Cardman, Lawrence S."],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2011,"date_issued":"2011-06-28T15:44:27Z","date_published":"2011-06-28T15:44:27Z","updated_at":"2026-07-22T22:25:24Z","subjects":["giant multipole resonances","lead-208","bremsstrahlung monochromator","scintillation detector"],"languages":["en"],"rights":["1979 Zane William Bell"],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["397412"],"render_values":[{"text":"397412","href":null,"code":true}]}]},"links":{"outbound_url":"http://hdl.handle.net/2142/25549","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Cardman, Lawrence S."]},{"key":"dc:creator","label":"Author","values":["Bell, Zane William"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2011-06-28T15:44:27Z","10000-01-01","1979"]},{"key":"dc:type","label":"Dc Type","values":["Dissertation / Thesis","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."]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["giant multipole resonances","lead-208","bremsstrahlung monochromator","scintillation detector"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["1979 Zane William Bell"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["397412","http://hdl.handle.net/2142/25549"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["\"The differential photoneutron cross section of 208pb in the energy region 9.9 through 11.2 MeV was measured with gamma energy resolution of approximately 100 KeV using the University of 111inois bremsstrahlung monochromator. Neutrons from a 72% enriched 208pb target and an 88% enriched 206po target were detected with an NE213 scintillation detector having a neutron energy resolution of 11.3 at 4 MeV, a 200 cm flight 'path, and an intrinsic time resolution of 1.6 ns. Neutrons leaving 207pb in its ground state and first two excited states were resolved and angular distributions for these partial cross sections were measured at seven angles from 450 to 1350 inclusive. The total photoabsorption cross section as well as the cross sections for leaving 207pb in its ground st ate and first two excited states were extracted. The data confirm the fine structure seen in earlier photoneutron studies and this structure is found to be mainly electric dipole in character. This assignment is consistent with the results of a recent elastic photon scattering study but inconsistent with an interpretation that ma~es an isovector E2 assignment based on inelastic electron scattering data. The observed integrated g1 strength in the energy region under study is consistent with the amount implied by the tail of a Lorentz line fit to earlier photoneutron data. The present data show local concentrations. and depletions of dipole strength rather than additional strength. The partial cross sections for leaving 207pb in its ground state and first two excited states were analyzed using the statistical compound nucleus model. The data indicate that this model does not correctly describe the branching to the lowest states of 207~b and that the relative amplitudes of the particle-hole states that contribute to the excited states of 208pb are not equal. The 312-hole state is found to dominate the emission process. Only moderate agreement with the observed branching is obtained by allowing for variations among the eight one particle one hole mulitudes that contribute to the decay of 208pb . It is shown that there must be a small g-wave component in the decay to the first excited state of 207 pb . The data, however, cannot be used to determine these amplitudes because there are only three measured cross sections. The experiment can only act as a \"\"necessary\"\" condition for a microscopic description of the excited states of 20Spb in this energy region. Lastly, a calculation of the angular distributions using the Direct-Semi-Direct excitation model and including a broad ( = 2.6 MeV) E2 resonance is not inconsistent with previous suggestions of such a resonance at 10.S MeV.\"","Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-28T15:44:27Z No. of bitstreams: 1 1979_bell.pdf: 5604016 bytes, checksum: 36cfab6586ad30cf23b662e7e596a81c (MD5)","Made available in DSpace on 2011-06-28T15:44:27Z (GMT). No. of bitstreams: 1 1979_bell.pdf: 5604016 bytes, checksum: 36cfab6586ad30cf23b662e7e596a81c (MD5) Previous issue date: 1979","Restriction data tranferred 2014-07-01T11:32:25-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-28T15:44:27Z Item is restricted indefinitely.","Thesis","U of I Only"]},{"key":"dc:title","label":"Title","values":["Giant multipole resonances in lead-208"]}]}],"canonical_facts":{"dc:contributor":["Cardman, Lawrence S."],"dc:creator":["Bell, Zane William"],"dc:date":["2011-06-28T15:44:27Z","10000-01-01","1979"],"dc:description":["\"The differential photoneutron cross section of 208pb in the energy region 9.9 through 11.2 MeV was measured with gamma energy resolution of approximately 100 KeV using the University of 111inois bremsstrahlung monochromator. Neutrons from a 72% enriched 208pb target and an 88% enriched 206po target were detected with an NE213 scintillation detector having a neutron energy resolution of 11.3 at 4 MeV, a 200 cm flight 'path, and an intrinsic time resolution of 1.6 ns. Neutrons leaving 207pb in its ground state and first two excited states were resolved and angular distributions for these partial cross sections were measured at seven angles from 450 to 1350 inclusive. The total photoabsorption cross section as well as the cross sections for leaving 207pb in its ground st ate and first two excited states were extracted. The data confirm the fine structure seen in earlier photoneutron studies and this structure is found to be mainly electric dipole in character. This assignment is consistent with the results of a recent elastic photon scattering study but inconsistent with an interpretation that ma~es an isovector E2 assignment based on inelastic electron scattering data. The observed integrated g1 strength in the energy region under study is consistent with the amount implied by the tail of a Lorentz line fit to earlier photoneutron data. The present data show local concentrations. and depletions of dipole strength rather than additional strength. The partial cross sections for leaving 207pb in its ground state and first two excited states were analyzed using the statistical compound nucleus model. The data indicate that this model does not correctly describe the branching to the lowest states of 207~b and that the relative amplitudes of the particle-hole states that contribute to the excited states of 208pb are not equal. The 312-hole state is found to dominate the emission process. Only moderate agreement with the observed branching is obtained by allowing for variations among the eight one particle one hole mulitudes that contribute to the decay of 208pb . It is shown that there must be a small g-wave component in the decay to the first excited state of 207 pb . The data, however, cannot be used to determine these amplitudes because there are only three measured cross sections. The experiment can only act as a \"\"necessary\"\" condition for a microscopic description of the excited states of 20Spb in this energy region. Lastly, a calculation of the angular distributions using the Direct-Semi-Direct excitation model and including a broad ( = 2.6 MeV) E2 resonance is not inconsistent with previous suggestions of such a resonance at 10.S MeV.\"","Submitted by Carolyn Mead (cmead2@illinois.edu) on 2011-06-28T15:44:27Z No. of bitstreams: 1 1979_bell.pdf: 5604016 bytes, checksum: 36cfab6586ad30cf23b662e7e596a81c (MD5)","Made available in DSpace on 2011-06-28T15:44:27Z (GMT). No. of bitstreams: 1 1979_bell.pdf: 5604016 bytes, checksum: 36cfab6586ad30cf23b662e7e596a81c (MD5) Previous issue date: 1979","Restriction data tranferred 2014-07-01T11:32:25-05:00 Original Data Group with Access UIUC Users [automated] Release Date: none Reason: Thesis","Item marked as restricted to the 'UIUC Users [automated]' Group (id=2) by Carolyn Mead (cmead2@illinois.edu) on 2011-06-28T15:44:27Z Item is restricted indefinitely.","Thesis","U of I Only"],"dc:identifier":["397412","http://hdl.handle.net/2142/25549"],"dc:language":["en"],"dc:rights":["1979 Zane William Bell"],"dc:subject":["giant multipole resonances","lead-208","bremsstrahlung monochromator","scintillation detector"],"dc:title":["Giant multipole resonances in lead-208"],"dc:type":["Dissertation / Thesis","text"],"thesis:degree_discipline":["Physics"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."]},"updated_at":"2026-07-22T22:25:24Z"}