Alpha and Gamma-ray Spectroscopic Studies of Au, Pt, and Ir Nuclei Near the Proton Dripline

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 i_13/2 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.