Rotational bands representing a multiplicity of shapes in ¹²⁷⁻¹³¹Pr

Author

Bradley Hagood Smith

Date of Award

12-1998

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

Lee L. Riedinger

Committee Members

Witek Nazarewicz, Carrol Bingham, Robert Compton

Abstract

High spin states of several isotopes of Praesyodimium (Z = 59) have been studied. Rotational bands representing well deformed shapes (enhanced deformaiton) have been observed in all the nuclei^{127-131Pr. In addition, a set of four new sequences of γ rays has been identified as superdeformed bands and assigned to the odd-A nucleus 131Pr. The observation of enhanced deformed (ED) bands in both 127Pr and 128Pr extends the knowledge of such bands to the lightest isotopes of Pr yet. Significant new extensions to the level schemes of previously known nuclei such as 130Pr have been made in this work. Furthermore, a total of five rotational band structures including the ED bands have been assigned to 128Pr. Prior to this work, only the lowest few high-spin states in the yrast band of 128Pr had been reported. The bands observed in odd-odd nuclei, 128,130Pr are generally based on the proton states πh_11/2 and πg_9/2coupled to the neutron states vh_11/2, vd_5/2, and vg_7/2. In the odd-A nuclei, 129,131Pr, the ground state bands arise from a πd_5/2 orbital, and the SD bands of 131Pr are thought to involve not only the πg_9/2 but also the intruder orbital vi_13/2 An experiment using the heavy-ion fusion reaction 94Mo(40Cl) at 180 MeV was carried out at the Lawrence Berkeley Laboratory to populate high-spin states in the abovementioned nuclei. The gammasphere Compton-suppressed Ge detector array was used in conjunction with the Microball charged particle detection system. Highly correlated γ-ray and charged particle events were recorded to tape. In subse-quent offline analysis, which is the subject of this dissertation, the (3p, xn) channel yielded high spin structure data for 131-129Pr. Analysis of the (1p, 1α, xn) channel provided results for 129-127Pr and the (2p, xn) channel for 130Nd. A wide variety of physical quantities have been extracted from the level schemes of the Pr nuclei. Extracted experimental band-crossing frequencies, ħω_c, for example, have been compared with ħω_c calculated using a cranked Woods-Saxon potential (CSM) to investigate quasiparticle configuration assignments. Also, a trans-formation of the energies of states in each signature from coupled bands has been used to study relationships between the two signatures of such bands. Prom this trans-formation, the known signature inversion of πh_11/211/2 bands in doubly-odd Pr nuclei has been confirmed in 132,130Pr and newly identified in 128Pr. A systematic comparison of measured and calculated dynamic moments of inertia and J(2) and β₂ de-formations is made for πg_9/2 bands. Prom this comparison, it is surmised that the normal deformed structures experience a systematic increase in deformation with de creasing neutron number (N) in agreement with theoretical predictions. Also, from systematic changes in J(2) consistent with the previous statement, it appears that the ED rotational bands exhibit a decrease in the enhancement of deformation as N decreases. In addition to these physics results, the analysis section of this dissertation presents procedures for analyzing data from the Microball combined with GAMMA-SPHERE. Analysis of charged particle data from the Microball is complicated. The procedures outlined in the experimental procedures of this work may prove useful as a guide for future studies involving similar experimental configurations.}

Recommended Citation

Smith, Bradley Hagood, "Rotational bands representing a multiplicity of shapes in ¹²⁷⁻¹³¹Pr. " PhD diss., University of Tennessee, 1998.
https://trace.tennessee.edu/utk_graddiss/9364