Browsing by Author "Brits, Christiaan Petrus"

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    Coulomb excitation of the 2+ state in 14C and the quadrupole deformation of states in 194Pt
    (Stellenbosch : Stellenbosch University, 2019-12) Brits, Christiaan Petrus; Wiedeking, Mathis; Hadynska-Kl¸ek, Katarzyna; Papka, Paul; Stellenbosch University. Faculty of Science. Dept. of Physics.
    ENGLISH ABSTRACT: The safe Coulomb excitation experiment of 14C and 194Pt which took place at Florida State University took advantage of the unique beam capabilities, the availability of highefficiency large volume LaBr3(Ce) detectors and the S3 double sided silicon strip detector. Using the advantageous experimental environment the B(E2: 2+1 ! 0+1 ) value of the firstexcited 2+1 state of 14C and the quadrupole deformation of states in 194Pt are investigated. B(E2: 2+1 ! 0+1 ) values of neutron-rich even-even C isotopes have been reported up to 20C and provide important information on the evolution of the underlying structural mechanism towards the drip line. They also provide critical constraints for theoretical models as is the case for the experimentally determined B(E2: 2+1 ! 0+1 ) value for 14C which exhibits persistent inconsistencies with that obtained from theoretical models. The B(E2: 2+1 ! 0+1 ) value in 14C cannot be reproduced by theoretical models making it indispensable to enhance our theoretical understanding of the C isotopic chain in general. The 2+1 state was not observed in the particle- data, which may indicate that 14C undergoes single-particle excitation and has a smaller B(E2: 2+1 ! 0+1 ) value than previously thought. The A 190 region is very interesting since it has oblate, prolate, -soft and spherical shaped nuclei. It is predicted that Pt evolves from prolate deformed 180􀀀186Pt to -soft 188Pt and triaxial 190Pt to oblate 192􀀀198Pt and finally to spherical 204Pt. From this work, the quadrupole deformation of the 0+1 , 2+1 , 4+1 , 2+2 , 4+2 states are successfully measured with increased accuracy. Additionally it is determined that 194Pt is triaxial oblate which supports the theoretical prediction of the shape evolution in Pt.
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    Search for the scissors resonance in 182Ta
    (Stellenbosch : Stellenbosch University, 2016-12) Brits, Christiaan Petrus; Wiedeking, Mathis; Kheswa, Bonginkosi V; Papka, Paul; Stellenbosch University. Faculty of Science. Dept. of Physics
    ENGLISH ABSTRACT :Relatively small changes to the overall shape of the photon strength function such as the scissors or pygmy resonances can have a significant impact on reaction rates. Reaction rates are important for modeling processes that take place in astrophysical environments and nuclear reactors. Recent results indicate the existence of a significant amount of scissors resonance strength in the photon strength function for nuclei in the actinide region. In order to investigate the extent and persistence of the scissors resonance strength towards lighter nuclei, an experiment was performed utilizing the NaI(Tl) gamma-ray detector array (CACTUS) and silicon particle telescopes (SiRi) at the cyclotron laboratory at the University of Oslo. Particle-gamma coincidences from the 181Ta(d,p)182Ta and 181Ta(d,d’)181Ta reactions were used to measure the nuclear level density and photon strength function of the well-deformed 182Ta and 181Ta systems. From these data (n, ) cross sections were calculated with the Talys reaction code. While there are possible bumps in the photon strength function of 181Ta that may be due to the scissors resonance, it appears to be absent for 182Ta. These results are discussed in the context of nuclear structure and other work done in this and other mass regions.