Date of Award

5-2004

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Leo L. Riedinger

Committee Members

Carol Bingham, Witek Nazarewicz, Rick Williams

Abstract

This dissertation reports the observation of α-decay and in-beam level structures in the neutron-deficient nuclei 176,174Au, 173,174Pt, and 175Ir from an experiment which was performed at Argonne National Laboratory (ANL). A beam of 84Sr projectiles was used to bombard 92,94,96Mo targets. From these reactions, the 176,178,180Hg compound nuclei were made which eventually decayed into more than 20 product nuclei. The experiment was performed with the Atlas accelerator and utilized the Gammasphere array at the target position in conjunction with the Fragment Mass Analyzer (FMA) for mass identification and a Double-Sided Silicon Strip Detector (DSSD), which was used to observe the recoiling implants and the alpha particles associated with each nuclide.

The Recoil Decay Tagging method (RDT) was sued to study high-spin states in 174Pt populated via the 92Mo(84Sr,2p) and 94Mo(84Sr,2p2n) reactions. The ground-state rotational band of levels has been extended from I = 14 to 24 (tentatively 26) and a new side band is observed up to a spin of 21 (tentatively 23). A change or band crossing is observed in the latter structure at a low rotational frequency which is similar to that seen in the ground-state band. The first and second i13/2 neutron alignment processes are observed for the first time in 174Pt. Surprisingly, these crossings occur at approximately the same rotational frequency. Total Routhian Surface and Cranked Shell Model calculations are used in an attempt to understand this behavior.

The α-decay properties of 174,176Au, 175Ir, and 173Pt were studied following the 92Mo(84Sr,pn), 94Mo(84Sr,pn), 94Mo(84Sr,3p), and 92Mo(84Sr,2pn) reactions, respectively. Correlations between first- and second-generation α decays and γ-ray transitions in daughter nuclei were measured, giving evidence for fine structure α peaks in these odd-odd gold nuclei. Inverse RDT was used to provide further collaborating evidence. Four α decay lines, including three new transitions, were observed and assigned to 176Au. 174Au was observed to have four α decay lines including two newly discovered transitions. In addition, excited states in 174,176Au and 172Ir have been observed for the first time by use of RDT method. Spin and configuration assignments are discussed.

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