Final PhD Oral Examination (Thesis Title: “Single Particle Structure of Exotic Strontium Isotopes”)

Speaker: 
STEFFEN JAMES CRUZ
Event Date and Time: 
Thu, 2017-05-25 12:30 - 14:30
Location: 
Room 202, Anthropology and Sociology Building
Local Contact: 
Physics and Astronomy, UBC
Intended Audience: 
Public

Abstract:
The sudden onset of ground state deformation and the emergence of shape-coexisting states in the vicinity of N~60 and Z~40 has been a subject of substantial interest for many years. It has been shown that the emergence of deformed low-energy configurations can be explained in the shell model by the evolution of single particle structure and the interaction between protons and neutrons in certain valence orbitals. However, the numerous theoretical models that have been developed for this transitional region are limited by the experimental data that is available. In particular, a description of the underlying single particle configurations of low energy states is essential for a detailed description of this region.

In this work, the single particle structure of states in ⁹⁵Sr and ⁹⁶Sr has been investigated through the one-neutron transfer reactions ⁹⁴Sr(d,p) and ⁹⁵Sr(d,p) in inverse kinematics at TRIUMF. In each of these experiments, a 5.5 MeV/u Sr beam was impinged on a 5.0 mg/cm2 CD2 target, and emitted particles and gamma rays were detected using the SHARC and TIGRESS detector arrays, respectively. Using an angular distribution analysis, firm spin assignments have been made for the first time of the low-lying 352 keV, 556 keV and 681 keV excited states in ⁹⁵Sr from ⁹⁴Sr(d,p), and a constraint has been made on the spin of the higher-lying 1666 keV excited state in ⁹⁵Sr. Similarly, angular distributions have been extracted for 14 states in ⁹⁶Sr from ⁹⁵Sr(d,p), and new experimental constraints have been assigned to the spins and parities of 8 states in ⁹⁶Sr. Additionally, two new states in ⁹⁶Sr have been identified in this work. A measurement of the mixing strength between the 1229 keV and 1465 keV shape-coexisting 0⁺ states in ⁹⁶Sr was also made, which was found to be a2=0.48(17).

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