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Title: Lifetime measurements probing shape coexistence in 175Au, 174Pt and 175Pt
Author: Watkins, Heidi
ISNI:       0000 0004 2703 7153
Awarding Body: University of Liverpool
Current Institution: University of Liverpool
Date of Award: 2011
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For the first time, lifetime measurements of the excited states in 175Au, 174Pt and 175Pt have been measured using the recoil-decay tagging technique in recoil distance Doppler-shift measurements. These states were populated by a fusion-evaporation reaction using a 92Mo target and a 401 MeV 86Sr16+ beam. This work was carried out at the Accelerator laboratory of the University of Jyvaskyla, Finland, where a plunger device has been coupled to the JUROGAM detector array and the RITU gasfilled separator. The present study addresses the phenomenon of shape coexistence in neutron deficient nuclei below the Z = 82 closed shell. Lifetimes of the low-lying excited states in the very neutron-deficient nucleus 175Au have been measured. Transitional quadrupole moments and reduced transition probabilities extracted for this odd-Z nucleus provide evidence for the existence of three distinct shapes and indicate the transition between collective and non collective structures. These measurements constitute the first deformation measurements of triple shape coexistence in a heavy odd-Z nucleus. The results are compared to the available lifetime measurements for Hg and Tl nuclei. A lifetime of the 6+ yrast state in 174Pt has been measured using recoil-decay tagged γ-ray spectra. In addition, lifetimes of the 17/2+ and 21/2+ yrast states in 175Pt have been measured using recoil-gated γγ-coincidence spectra. Transitional quadrupole moments and deformation parameters extracted for these nuclei provide information on the change in nuclear shape resulting from the mixing of different shaped configurations at low spin. The results are compared to TRS calculations produced for neutron deficient Pt nuclei below the neutron N = 104 mid-shell.
Supervisor: Page, Robert ; Joss, David Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
Keywords: QC Physics