Browsing by Author "Dr. Gary E. Mitchell, Committee Co-Chair"

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    A High Resolution Study of p + 44Ca Reactions
    (2004-05-12) Lokitz, Stephen Jared; Dr. Gary E. Mitchell, Committee Co-Chair; Dr. John F. Shriner, Jr., Committee Co-Chair; Dr. Mohamed Bourham, Committee Member; Dr. John H. Kelley, Committee Member
    A high resolution measurement of the cross-sections of the 44Ca(p,p0) and 44Ca(p,p1) reactions was performed over the energy range E[subscript p] = 2.50--3.53 MeV to improve the purity and completeness of the 45Sc level sequences. A specific goal was the investigation of possible parity-dependence of the level densities of 45Sc. This research was performed at the High Resolution Laboratory at Triangle Universities Nuclear Laboratory. The data were measured at five angles and the observed cross-sections were fit with the multilevel, multichannel, R-matrix code MULTI6. Many levels were observed for the first time, and many levels were reassigned different quantum numbers. A total of ~800 resonances were observed. The purity and completeness of the 45Sc data were tested via several statistical analyses: the nearest-neighbor spacing distribution, the reduced width distribution, and the Dyson-Mehta Δ₃ statistic. The results of the statistical analyses were mixed. The s-wave resonance sequence compares very well with random matrix predictions. The other sequences do not agree well with GOE predictions, suggesting missing and/or misassigned levels. The experimental nearest-neighbor spacings were compared to the Wigner distribution to identify anomalously large (small) spacings which imply missing (misassigned) levels. The number of anomalous spacings has been reduced, indicating improved purity and completeness of the data. In particular the small spacing anomalies proved to be a very useful and practical analysis tool. The level densities were determined using two methods to correct for missing levels. Uncertainties in the level densities have been significantly reduced. No evidence of parity dependence in the level densities of 45Sc was observed.
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    A High Resolution Study of Proton Resonances in 51Mn
    (2004-08-16) Beal, William Chandler; Dr. Mohamed Bourham, Committee Member; Dr. Gary E. Mitchell, Committee Co-Chair; Dr. John F. Shriner, Jr., Committee Co-Chair; Dr. D. Ronald Tilley, Committee Member
    High-resolution measurements of the differential cross sections of the 50Cr(p,p0) and 50Cr(p,p1) reactions were performed over the energy range E[subscript p]=1.8045–3.5011 MeV at five different scattering angles. This experiment was performed at the High Resolution Laboratory (HRL) at Triangle Universities Nuclear Laboratory (TUNL); the system is capable of measuring proton-scattering data with an energy resolution of ~250 eV. The goal of this work is to improve the purity and completeness of the 51Mn level sequences in order to investigate average level properties. The observed cross sections were fit using the multi-level, multi-channel, R-matrix code MULTI, and resonance parameters were extracted from the data. Many resonances were observed for the first time, and several others were reassigned different quantum numbers compared to previous work. A total of 185 resonances were observed, 64 of which had not been observed in previous studies. Statistical analyses based on predictions of random matrix theory were performed on the nearest-neighbor spacing distributions and the reduced-width distributions, with mixed results. The s-wave resonance sequences are in good agreement with GOE predictions, while the p-wave resonance analyses show evidence of missing and misassigned levels. Separation of the d-wave, f-wave, and g-wave resonances into pure sequences is not feasible due to ambiguity in J assignments for these levels. Strength functions and level densities were determined for both the pure and mixed sequences.