Departmental Oral Examination (Thesis Title: “Decay spectroscopy of N ~ Z nuclei in the vicinity of 100Sn”)

Event Date and Time: 
Thu, 2017-01-12 16:00 - 18:00
Henn 318
Local Contact: 
Physics and Astronomy, UBC
Intended Audience: 

The nuclear shell model (SM) has been very successful in describing the properties and the structure of near-stable and stable isotopes near the magic nuclei. Today, the advent of powerful facilities capable of producing radioactive isotopes far from stability has enabled the test of the SM on very proton-rich or neutron-rich magic nuclei. 100Sn is a proton-rich doubly-magic nucleus, but is nearly unstable against proton emission. Key topics of nuclear structure in this region include the location of the proton dripline, the effect of proton-neutron interactions in N ~ Z nuclei, single-particle energies of orbitals above and below the N = Z = 50 shell gaps, and the properties of the superallowed Gamow-Teller decay of 100Sn.

A decay spectroscopy experiment was performed on 100Sn and nuclei in its vicinity at the RIKEN Nishina Center in June 2013. The isotopes of interest were produced from fragmentation reactions of 124Xe on a 9Be target, and were separated and identified on an event-by-event basis. Decay spectroscopy was performed by implanting the radioactive isotopes in the Si detector array (WAS3ABi) and observing their subsequent decay radiations. Positrons and protons were detected by WAS3ABi, and the gamma rays were detected by a high-purity Ge detector array (EURICA).

Of the proton-rich isotopes produced in this experiment, over 20 isotopes as light as 88Zr and as heavy as 101Sn were individually studied. New and improved measurements of isotope/isomer half-lives, beta-decay endpoint energies, beta-delayed proton emission branching ratios, and gamma-ray transitions were analyzed. In general the new results were well reproduced by the SM, highlighting a relatively robust 100Sn core. However, the level scheme of 100Sn's beta-decay daughter nucleus 100In was not conclusively determined because of several missing observations which were expected from various SM predictions. Significantly higher beta-decay and gamma-ray statistics are required on several nuclei, including 100Sn, to evaluate the limit of the current understanding of their structure.

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