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Title: Multiparticle configurations in 155Lu (N = 84) and 158Ta (N = 85)
Author: Carroll, Robert
ISNI:       0000 0004 2724 7177
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2012
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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.
Supervisor: Joss, David. ; Page, Robert. Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QC Physics