Nuclei in the light rare-earth, for values of N ≥ 90, are textbook examples of the evolution of nuclear structure with respect to excitation energy and angular momentum in deformed nuclei. In the high-spin region (J ≥ 10ħ), effects such as backbends and shape changes occur, ending with termination of the lower energy collective structures. %First backbends occur before 20hbar Findings also reflect a spectacular return to collectivity in the ``ultra-high spin'' region (J ≥ 50ħ). Thanks to recent developments in both detectors and accelerators, gamma-ray spectroscopy has been able to probe the upper ends of the high-spin region, and begin probing into the ultra-high spin regime.
Data from two experiments form the basis of this work. One study was an ultra-high-spin analysis of the Z = 67, N = 90 157Ho nucleus at Argonne National Laboratory with Gammasphere. The findings were that remarkable correlations were observed to the neighboring isotone, 158Er, in which termination states and ultra-high spin structures had been previously observed. A high-spin investigation of Ytterbium (Yb) and Erbium (Er) isotopes was performed at FSU. This study used an intense radioactive 14C beam, available at FSU, in order to study these heavy, neutron-rich nuclei in regions of angular momentum and excitation energy not attainable with stable beams. The reactions of 170Er(14C,5n/4n/α4n) generated new information in 169Yb, 170Yb, and 166Er, respectively. Due to the recently upgraded digital FSU Gamma-Ray Array, aided by JBSMILE, triple γ-ray coincidences were able to be viewed in these nuclei for the first time at FSU. The result was the investigation of rotational alignments in both the yrast and non-yrast multi-quasiparticle bands in these nuclei.
|Advisor:||Riley, Mark A.|
|Commitee:||Reina, Laura, Steinbock, Oliver, Tabor, Samuel L., Volya, Alexander|
|School:||The Florida State University|
|School Location:||United States -- Florida|
|Source:||DAI-B 80/06(E), Dissertation Abstracts International|
|Subjects:||Physics, Nuclear physics|
|Keywords:||157Ho, 166Er, 169,170Yb, Angular momentum, Evolution of nuclear structure, Excitation energy, Exotic nuclear deformation|
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