The structure of ²³Al and astrophysical consequences /
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| Other Authors: | |
| Format: | Thesis eBook |
| Language: | English |
| Published: |
[College Station, Tex.] :
[Texas A&M University],
[2010]
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| Subjects: | |
| Online Access: | Link to OAK Trust copy |
| Abstract: | Motivated by existing nuclear astrophysics problems, the [beta]-decay of the proton rich nucleus ²³Al was studied for the first time with pure samples which were obtained by using the ¹H(²⁴Mg,²³Al)2n reaction and the MARS recoil separator at Texas A&M University. [Beta] and [beta-gamma] coincidence measurements were made with a fast tape-transport system, scintillator, BGO and HPGe [gamma] detectors. The experiment allowed us to measure absolute [beta] branching ratios and to determine logft values for transitions to final states in ²³Mg, including the isobaric analog state (IAS), and, therefore, to determine unambiguously the spin and parity of the ²³Al ground state to be J^Pi = 5/2+. This work excludes the large increases in the radiative proton capture cross section for the reaction ²²Mg([pi,gamma])²³Al at astrophysical energies, which were implied by claims that the spin and parity of the ²³Al ground state were J^Pi = 1/2+. More precise half life and mass determinations of ²³Al were obtained from the experimental data. The logft for the Fermi transition to its isobaric analog state in ²³Mg was also determined for the first time. This IAS and a state 16 keV below it were observed, well separated in the same experiment for the first time. The [beta]-decay scheme of the proton rich nucleus ²³Al was established. We can now solve a number of inconsistencies in the literature, exclude strong isospin mixing claimed before, and obtain a new determination of the resonance strength. The IAS and the state 16 keV below it are resonances in the ²²Na([pi,gamma])²³ Mg reaction at energies that are important in novae. This second state turns out to be the resonance that gives the most important contribution in the depletion of ²²Na from novae. Both of the reactions of ²²Mg([pi,gamma])²³Al and ²²Na([pi,gamma])²³Mg have been suggested as possible candidates for diverting some of the flux in oxygen-neon novae explosions from the A=22 into the A=23 mass chain. |
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| Item Description: | "Major Subject: Physics" Title from author supplied metadata (automated record created 2010-03-12 12:08:51). Electronic resource. |
| Physical Description: | 1 online resource. |
| Bibliography: | Includes bibliographical references. |