Browsing by Author "Mdletshe, Linda"

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    Search for Collective Strutures in the 186Os And 150Gd Nuclei
    (University of Zululand, 2021) Mdletshe, Linda
    Despite the extensive experimental and theoretical studies that have been conducted onthe low-lying positive-parity 0+2, 2+2, and 4+3states in the transitional deformed nuclei,their microscopic identity remains unclear. It is still one of the major challenges innuclear structure physics to properly understand the nature of these states. To givemore insight on the underlying nature of such states, the excited bands in186Os and150Gd nuclei were investigated at iThemba laboratory for accelerator based sciences(iThemba LABS) using the186W(4He, 4n)186Os and150Sm(4He, 4n)150Gd reactions.The AFRODITEγ-ray spectrometer was used for detection ofγ-ray energies emittedduring the experiments.The decay scheme of186Os has been improved. In particular, a total of 21 newγ-raytransitions have been added to the level scheme of186Os. Most importantly, bandsbuilt on the excited 0+2, 2+2, and 4+3states have not only been confirmed but extendedup to spins of 12+, 15+, and 8+, respectively. In addition, a number of new linkingtransitions were identified. Angular distribution and linear polarization measurementswere employed to accurately assign spins and parities to the known and new levels in186Os. The properties of the excited states in186Os, such as level energies and branch-ing ratios, are interpreted in the context of the systematics of neighboring even-even182−192Os isotopes. Furthermore, the validity of theK-selection rule which emanatesfrom a description based on an axially symmetric nuclear shape is examined. The ob-served decays between the rotational bands support a description whereKis conserved.However, someK-forbidden decays were also identified, thus suggesting that a modelallowing for smallKadmixtures is probably required.The excited bands in this nucleus are compared with the five-dimensional collectiveHamiltonian calculations based on covariant density functional theory (5DCH-CDFT),calculations within the quasiparticle triaxial-rotor (QTR) model and predictions by asimple rotational-vibrational model. The 5DCH-CDFT calculations predict that thecollective structures are associated with different nuclear shapes, varying in quadrupoledeformation, triaxiality andγ-softness.The decay scheme of150Gd has been considerably extended. The data did not providenew information on the low-spin states, which was the initial aim of this experiment,however, 31 new transitions were identified at high spins. The present study for thesetransitions was confined toγ-coincidence analysis. The results for150Gd are presentedin the appendix section.
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    The study of low lying positive parity bands in 162Yb
    (University of Zululand, 2017) Mdletshe, Linda
    Over the last decade, iThemba LABS has had an active research program that focuses on the spectroscopy of low lying positive parity bands [1{8], particularly the so-called _ and vibrational bands, which are traditionally associated with the _rst excited K_ = 0+ and K_ = 2+ bands, respectively. Through this program, the nature of these bands has been studied extensively. However, despite this, the microscopic identity of these bands remains elusive in the transitional rare-earth region. This work seeks to give an insight on the microscopic nature of these bands by studying the spectroscopy of 162Yb. The data for the nucleus of interest (162Yb) was collected at iThemba LABS, using the 150Sm (16O, 4n) 162Yb fusion evapora- tion reaction. The rays emitted from the reaction products were detected using the AFRODITE ray spectrometer [9] equipped with escape-suppressed clover detectors. A total of 10 bands have been observed in this work. The DCO and polarization measurements have not only been used to con_rm assignments that were made by previous in-beam works on well established structures [10{12] - but have also been instrumental in the assignment of spins and parities for the majority of newly established bands in 162Yb. Further, the current study has not only con_rmed all the rotational structures reported by previous in-beam works but has also extended the level scheme of 162Yb by establishing 6 new bands. More importantly, a band built on the above-mentioned K_ = 0+ excitation has been identi_ed for the _rst time. In addition, for the _rst time in 162Yb, we also report rotational levels that form band structures of both the odd and even spin components of the K_ = 2+ vibrational band.