Gamma rays following the decay of <sup>160</sup>Tb and <sup> 188</sup>W were detected in both singles and coincidence in order to establish the energy level scheme of the two medium mass nuclei <sup>160</sup>Dy and 1880s. Two large volume Ge(Li) detectors together with a plastic scintillation counter were incorporated in a Dual Parameter Energy-Time Spectrometer to measure the gamma-gamma coincidence spectra: the half-life of the first excited state of <sup>160</sup>Dy was measured. An intrinsic Germanium detector was used to measure low energy transitions. New levels and transitions are proposed, relative intensities, log ft values, multipolarities, spins/parities and transition probabilities are deduced. The nuclear properties of <sup>160</sup>Dy and <sup>188</sup>Os are analysed in terms of current nuclear models. The deviations from the predictions of the symmetric rotor model for the states in <sup>160</sup>Dy are explained in terms of band-mixing. The Coriolis coupling is applied to the negative states which gives good account to the electric dipole transition probabilities. The possible effect of the recently discovered sub-shell closure at Z = 64 is investigated for <sup>160</sup>Dy, a nucleus with proton number (Z=66) exactly midway between the closures at 50 and 82, and the number of neutrons (N=94) above the limit of 90. Energy levels, B(E2) absolute values and ratios are compared with IBM-1 calculations assuming either a single Z = 50-82 shell or a subshell closure at Z = 64. The latter calculation improves agreement with experiment. The O(6) limit description is applied to the <sup>188</sup>Os nucleus. Particular attention is made to the 0<sup>+</sup> states and M1 transitions, the presence of which form the basic test for an 0(6) type nucleus. The calculations in the context of IBM-1 were undertaken with the aid of the computer codes PHINT and FBEM.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:704660 |
| Date | January 1984 |
| Creators | Ibrahim, Noorddin |
| Publisher | Royal Holloway, University of London |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://repository.royalholloway.ac.uk/items/4fab4765-1b36-4fc1-9bef-df8581afe2b2/1/ |
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