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Multiparticle configurations in 155Lu (N = 84) and 158Ta (N = 85)

Carroll, Robert (2012) Multiparticle configurations in 155Lu (N = 84) and 158Ta (N = 85). Doctoral thesis, University of Liverpool.

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Abstract

Excited states in 155Lu and 158Ta have been populated in fusion evaporation reactions at the Accelerator Laboratory at the University of Jyvaskyla. Gamma-ray spectroscopy techniques have been employed, using both the Jurogam spectrometer at the target position and the GREAT spectrometer at the focal plane of the RITU separator, and level schemes have been constructed. Gamma-ray spectroscopy performed on 155Lu has revealed new structures at high spin and has confirmed spin isomerism as the mechanism by which the decay of the 155m2Lu(25/2-) state is hindered. The previous level scheme has been revised and compared with systematic trends across N = 84 isotones. Single-particle configurations have been assigned to low-lying states and mechanisms expected to construct structures at higher spin are discussed. Previously, no excited states in the doubly odd 158Ta nucleus were known above the two low-lying alpha-decaying states, which are proton unbound. For the first time, excited states built on the 158m1Ta(9^+) alpha-decaying state have been observed. Comparisons with N = 85 isotones are made and the interactions between nucleons in the pi h_{11/2}, nu h_{9/2} and nu f_{7/2} orbitals are discussed. A new isomeric state, which decays by both alpha-particle and gamma-ray emission, has been observed at high spin in 158Ta. No proton decay is observed from this state, despite a large proton Q-value. This hindrance to proton decay can be understood to be an effect of the centrifugal barrier at high spin. This introduces the possibility of other high-spin isomers existing beyond both the proton and neutron drip lines.

Item Type:Thesis (Doctoral)
Uncontrolled Keywords:nuclear structure physics lutetium lu tantalum ta proton drip line
Subjects:Q Science > QC Physics
Departments, Research Centres and Related Units:Academic Faculties, Institutes and Research Centres > Faculty of Science > Department of Physics
Status:Unpublished
ID Code:6293
Deposited On:09 Aug 2012 11:57
Last Modified:09 Aug 2012 11:57

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