Doctoral Degrees (Physics)

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Browsing Doctoral Degrees (Physics) by Subject "12C nucleus"

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    Investigation of the 2+ Hoyle state candidates in 12C
    (Stellenbosch : Stellenbosch University, 2015-04) Nemulodi, Fhumulani; Papka, Paul; Neveling, Retief; Stellenbosch University. Faculty of Science. Dept. of Physics.
    ENGLISH ABSTRACT: Over the years the 12C nucleus has proved to be one of the most fascinating nuclei to study. This thesis attempts to provide answers regarding some of the open questions regarding certain structural properties of this nucleus. This is done by performing two independent experiments to measure the 12C excitation energy spectrum. The frst experiment was aimed at investigating the existence of the 11.16 MeV 2+ state claimed to exist in 12C. The measurement was performed with the K600 magnetic spectrometer at iThemba LABS, South Africa, using the 11B(3He,d) 12C reaction with a 44 MeV 3He beam at three different laboratory angles θlab = (25° , 30° , 35° ). The results obtained showed no evidence of such a state in 12C and it was concluded that no such state exist. The results also showed signatures of a 2+ state in the 10 MeV excitation energy region. This state is associated with the 2+ excitation of the well known Hoyle state reported to exist at this region. A second experiment was aimed at searching for the 2+ excitation of the Hoyle state in the 10 MeV excitation energy region. This was achieved by using the 14C(p,t) 12C[3α] reaction with a 66 MeV proton beam and observing tritons at a laboratory angle of θlab = 21° . The measurement was performed with the K600 magnetic spectrometer in conjunction with silicon detectors mounted inside the scattering chamber. The peak fitting analysis performed on a singles event spectrum showed evidence of the population of the 2+ state at Ex = 9.69 ± 0.11 MeV and width of Γ = 1.43 ± 0.22 MeV. These parameters appear to shift when the coincidence events are taken into account. The parameters obtained for decay to the 8Be ground state decay mode are Ex = 9.97 ± 0.20 MeV and Γ = 1.03 ± 0.21 MeV for energy and width respectively. Whereas, the parameters obtained by gating on other decay modes are Ex = 9.55 ± 0.22 MeV and Γ = 1.15 ± 0.24 MeV for energy and width respectively. The newly found state decays predominately via the 8Be ground state decay mode.