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Title: Study of isomers using reactions with a 178Hf beam
Author: Jones, Gareth
Awarding Body: University of Surrey
Current Institution: University of Surrey
Date of Award: 2006
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A pulsed 178Hf beam at an energy of 1150 MeV was used to initiate deep-inelastic reactions in a thick 208Pb target, in order to study high-/K isomers in 177,178Hf. Blocked BCS calculations predict high-if multi-quasiparticle states at Ipi = 43/2- and 45/2+ in 177Hf and Ipi = 19+ and 22- in 178Hf. These isomers were not observed in the experiment, however limits have been placed on the lifetime of the Kpi=19+ isomer for given excitation energies. The quality of the blocked BCS calculations has been evaluated and compared with configuration-constrained energy-surface calculations. Previously unobserved decay branches from high-K isomers in 177,179Hf have been identified, including the first highly K-forbidden M3 transition to be observed from a multi-quasiparticle state. Spin-trap isomers in near-spherical Z=51, Sb isotopes have been populated for the first time using fusion-fission reactions with a pulsed 178Hf beam at an energy of 1150 MeV, impinging upon a 27Al target. Gamma-rays were observed from the decay of T1/2 = 200(30) mus and 52(3)mus isomers with spins and parities Ipi = (25/2+) and (27/2+) in 121,123Sb respectively. These states are proposed to have aligned v(h11/2)2 configurations coupled to an odd proton (pid5/2 or pig7/2 in 121,123Sb respectively). Intermediate isomers were also identified at Ipi =19/2- (T1/2 = 8.2(2) ns) and (15/2-) (T1/2 =40(2) ns) in 121,123Sb respectively. Spins and parities of the states in these nuclei were obtained using a combination of angular correlation and internal conversion measurements. The configurations of states in these nuclei are compared with the systematics of neighbouring Sn isotones and other Sb isotopes. In a survey of other fusion-fission products, an T1/2 =18(5) ns isomer has been identified in 99Mo. The long lifetime of this level is ascribed to a hindered El transition from a state with configuration pi(g9/2)2 ⊗ vg7/2.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available