Browsing by Author "John F. Shriner, Jr., Committee Co-Chair"

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    A High Resolution Study of the 52Cr(p,p0) and 52Cr(p,p1) Reactions
    (2005-07-05) McLean, Lance; Gary E. Mitchell, Committee Co-Chair; John F. Shriner, Jr., Committee Co-Chair; D. Ronald Tilley, Committee Member; Mohamed Bourham, Committee Member
    High resolution measurements of the 52Cr(p,p0) and 52Cr(p,p1) cross sections were performed at the High Resolution Laboratory (HRL) of the Triangle Universities Nuclear Laboratory (TUNL). Results were obtained for the (p,p₀) reaction over the energy range E[subscript p] = 2.1039-3.4711 MeV and for the (p,p₁) reaction over the energy range E[subscript p] = 2.6101-3.4711 MeV. The primary goal was the improvement of the purity and completeness of the level sequences in ⁵³Mn. Excitation functions were generated at five angles for both reaction channels. Fits to the observed cross sections were obtained using the multi-channel, multi-level R-Matrix code, MULTI6. Jπ assignments have been given to 263 resonances. Many resonances were observed for the first time, and many previously observed levels were given new quantum number assignments. Level sequences of specific Jπ were evaluated for purity and completeness using statistical tests based on random matrix theory. Several Jπ assignments were revised after application of the statistical tests. The resulting nearest-neighbor spacing distributions were compared to the Wigner distribution, and the reduced width distributions were compared to the Porter-Thomas distribution. Estimates of the observed fraction of levels for each sequence were obtained using both the spacing and width distributions. Strength functions and level densities were determined for each J[superscript π] sequence. The data for J=Ω allow a test of whether the level density depends on parity; no parity dependence was observed.
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    Proton Radiative Capture on 48Ti
    (2003-12-04) McDevitt, Daniel Bruno; Dr. G.E. Mitchell, Committee Co-Chair; John F. Shriner, Jr., Committee Co-Chair; D. Ronald Tilley, Committee Member; Mohamed A. Bourham, Committee Member
    The 48Ti(p, gamma)49V reaction was studied in the energy range Ep = 2.0--2.8 MeV. This research was performed at the High Resolution Laboratory at Triangle Universities Nuclear Laboratory. Capture spectra were obtained for 27 compound nuclear resonances whose resonance parameters (energy, spin, parity, and particle widths) had been determined in earlier experiments. The gamma rays were measured with a Compton-suppressed HPGe detector. A total of ten 1/2+ resonances, nine 1/2- resonances and eight 3/2 - resonances were studied. The primary motivation for these measurements was to provide a data set suitable for testing the applicability of conventional statistical models in this mass region. A secondary motivation was to evaluate the 'low level population' method (which works very well in heavier nuclei) in this mass region. The relative populations of 10 of the first 12 excited states of 49V were determined (the relative populations of two of the low-lying states could not be obtained due to gamma-ray resolution limitations). The average relative populations were similar for the three types of resonances. The experimental relative populations were compared with calculations performed with the statistical model code DICEBOX. Results for a variety of radiative strength function models yielded qualitatively similar results. These simulations agree only qualitatively with the experimental relative populations. Although the simulations suggest that the low level population method may work in this nuclide, the experimental results are at best ambiguous. Thus the statistical approach provides a reasonable qualitative description (but not a quantitative description) of the relative population of low-lying states in 49V.