Octupole degrees of freedom in Uranium-230
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Date
2021
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University of Zululand
Abstract
The nuclei230U and232U were considered to possibly have tetrahedral shape because their negative-parity bands lacked in-band E2 transitions. From a study about the implications of tetrahedral shapein230U and232U [7], it was discovered that these bands were better described as octupole vibrations.This was concluded from the observation of the in-band E2 transitions from the negative-paritybands which contradicted the idea of tetrahedral shape. However, more in-band E2 transitions wereobserved in232U compared with230U where only one in-band E2 transition was observed.This study seeks to observe in-band E2 transitions from the low-lying negative-parity states of230U.The nucleus230U was produced and studied at iThemba LABS using the reaction232Th(α, 6n)230Uat 63 MeV beam energy. Gamma-rays from230U were detected and measured with AFRODITEcoupled to a recoil detector. The recoil detector was an essential tool in this measurement as ithelps to suppress fission background that is associated with this type of reaction. The negative-parity band was extended with two new tentative states. No in-band E2 transtions were observed inthe low-lying negative-parity states, and only one new tentative in-band E2 transition was observedfrom the new levels. Intrinsic dipole moments, energies of the observed states, and transitions arecompared to systematics of neighboring nuclei. Related similarities in the intrinsic dipole moments,and energies are noticed in the systematics. These results still support octupole deformation ratherthan tetrahedral deformation.
Description
A thesis submitted to the Faculty of Faculty of Science, Agriculture and Engineering in fulfilment of the requirements for the Degree of Science in the Department of Physics at the University of Zululand, South Africa, 2021.
Keywords
Octupole degrees, nuclei230U, 232U, Uranium-230