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UBC Theses and Dissertations

Decay spectroscopy of N ~ Z nuclei in the vicinity of ¹⁰⁰Sn Park, Joochun (Jason)


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. 100/50Sn50 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 124/54Xe on a 9/4Be 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. β⁺ particles and protons were detected by WAS3ABi, and γ rays were detected by a 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, β-decay endpoint energies, β-delayed proton emission branching ratios, and γ-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 β-decay daughter nucleus ¹⁰⁰In was not conclusively determined because of several missing observations which were expected from various SM predictions. Significantly higher β-decay and γ-ray statistics are required on several nuclei, including ¹⁰⁰Sn, to evaluate the limit of the current understanding of their structure.

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