Citation
McDonald, Arthur Bruce (1970) Excitation Energies and Decay Properties of T= 3/2 States in ¹⁷O, ¹⁷F and ²¹Na. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/P0TR-DH36. https://resolver.caltech.edu/CaltechTHESIS:08112015-113730783
Abstract
The two lowest T = 3/2 levels in 21Na have been studied in the 19F(3He, n), 20Ne (p,p) and 20Ne (p,p’) reactions, and their excitation energies, spins, parities and widths have been determined. In a separate investigation, branching ratios were measured for the isospin-nonconserving particle decays of the lowest T = 3/2 levels in 17O and 17F to the ground state and first two excited states of 16O, by studying the 15N(3He,n) 17F*(p) 16O and 18O(3He, α)17O*(n) 16O reactions.
The 19F(3He,n) 21Na reaction was studied at incident energies between 4.2 and 5.9 MeV using a pulsed-beam neutron-time-of-flight spectrometer. Two T = 3/2 levels were identified at excitation energies of 8.99 ± 0.05 MeV (J > ½) and 9.22 ± 0.015 MeV (J π = ½+, Γ ˂ 40 keV). The spins and parities were determined by a comparison of the measured angular distributions with the results of DWBA calculations.
These two levels were also obsesrved as isospin-forbidden resonances in the 20Ne(p,p) and 20Ne(p,p’) reactions. Excitation energies were measured and spins, parities, and widths were determined from a single level dispersion theory analysis. The following results were obtained:
Ex = 8.973 ± 0.007 MeV, J π = 5/2 + or 3/2+, Γ ≤ 1.2 keV,
Γpo = 0.1 ± 0.05 keV; Ex = 9.217 ± 0.007 MeV, Jπ = ½ +,
Γ = 2.3 ± 0.5 keV, Γpo = 1.1 ± 0.3 keV.
Isospin assignments were made on the basis of excitation energies, spins, parities, and widths.
Branching ratios for the isospin-nonconserving proton decays of the 11.20 MeV, T = 3/2 level in 17F were measured by the 15N(3He,n) 17 F*(p) 16O reaction to be 0.088 ± 0.016 to the ground state of 16O and 0.22 ± 0.04 to the unresolved 6.05 and 6.13 MeV levels of 16O. Branching ratios for the neutron decays of the analogous T = 3/2 level, at 11.08 MeV in 17O, were measured by the 16O(3He, α)17O*(n)16O reaction to be 0.91 ± 0.15 to the ground state of 16O and 0.05 ± 0.02 to the unresolved 6.05 and 6.13 MeV states. By comparing the ratios of reduced widths for the mirror decays, the form of the isospin impurity in the T = 3/2 levels is shown to depend on Tz.
Item Type: | Thesis (Dissertation (Ph.D.)) | ||||||
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Subject Keywords: | (Physics) | ||||||
Degree Grantor: | California Institute of Technology | ||||||
Division: | Physics, Mathematics and Astronomy | ||||||
Major Option: | Physics | ||||||
Awards: | The Nobel Prize in Physics, 2015. Caltech Distinguished Alumni Award, 2018. | ||||||
Thesis Availability: | Public (worldwide access) | ||||||
Research Advisor(s): |
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Group: | Nobel Prize, Caltech Distinguished Alumni Award | ||||||
Thesis Committee: |
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Defense Date: | 14 July 1969 | ||||||
Additional Information: | The Nobel Prize in Physics 2015 was awarded jointly to Takaaki Kajita and Arthur B. McDonald "for the discovery of neutrino oscillations, which shows that neutrinos have mass." | ||||||
Funders: |
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Record Number: | CaltechTHESIS:08112015-113730783 | ||||||
Persistent URL: | https://resolver.caltech.edu/CaltechTHESIS:08112015-113730783 | ||||||
DOI: | 10.7907/P0TR-DH36 | ||||||
Related URLs: |
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Default Usage Policy: | No commercial reproduction, distribution, display or performance rights in this work are provided. | ||||||
ID Code: | 9095 | ||||||
Collection: | CaltechTHESIS | ||||||
Deposited By: | INVALID USER | ||||||
Deposited On: | 13 Aug 2015 22:25 | ||||||
Last Modified: | 16 May 2024 23:56 |
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