Alignment processes and shape variations in 184Pt and 183Au

Author

Michael Patten Carpenter

Date of Award

3-1988

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Leo L. Riedinger

Committee Members

C. R. Bingham, M. W. Guidry

Abstract

High-spin states in the transitional nuclei ¹⁸⁴Pt and ¹⁸³Au were measured via heavy-ion induced reactions. The three reactions used to study ¹⁸⁴Pt,^{172Yb(16O,4n)184Pt, 154Sm(34S,4n)184Pt and 160Yb(29Si,4n)184Pt, were run at beam energies ranging from 91 to 163 MeV. High-spin states in 183Au were populated using the 152Sm(35Cl,4n)184Pt reaction at 170 MeV. These measurements were performed at three separate facilities, the Holifield Institute for Heavy-Ion Re search, McMaster University Tandem Laboratory, and Chalk River Laboratory, using multi-detector γ-ray spectrometers of varied sophistication.}

Nuclear levels up to 37 fi have been measured in ¹⁸⁴Pt. Six new side bands have been identified, and the spins and parities in five of these bands have been firmly established. Four of these side are associated with two-quasineutron configurations, while another side band has been assigned a two-quasiproton configuration.

Levels in ¹⁸³Au have been observed up to 61/2 h. This work represents the first in-beam measurement performed on this nucleus. Four rotational bands have been identified. Two of these structures have been associated with the ½[541] Nilsson configuration, and the other two bands have been assigned the ½[530] and ½[660] configurations. While heavier Au isotopes have identified rotational bands built on the 11/2 [505] Nilsson configuration, such a band has not bee observed in the present data on ¹⁸³Au.

From the present work, strong evidence has been found which indicates that both πh_9/2 (½[541]) and vi_13/2 (9/2 [624]) quasiparticle alignments are occuring at low rotational frequencies in Pt and Au nuclei at N = 104 to 108. Since both pairs of quasiparticles occupy different states relative to the Fermi surface, they will polarize the nuclear core in opposite directions in the γ degree of freedom. Conclusions about the dependence of shape on these alignments comes from com- parison of the spectroscopic data with a set of Cranked Hartree-Fock Bogolyubov calculations, which are performed using the shell correction method. Discrepancies between the present experimental evidence and theoretical predictions are also noted and suggestions for a possible resolution to these differences are also presented.

Recommended Citation

Carpenter, Michael Patten, "Alignment processes and shape variations in 184Pt and 183Au. " PhD diss., University of Tennessee, 1988.
https://trace.tennessee.edu/utk_graddiss/11833