Degree

Doctor of Philosophy (PhD)

Department

Physics & Astronomy

Document Type

Dissertation

Abstract

Classical novae and Type I X-ray bursts are stellar explosions that occur in binary systems, where nuclear reactions involving 19Ne play a crucial role in nucleosynthesis. In novae, the destruction of 18F via the 18F(p,alpha)15O reaction significantly affects the amount of 18F remaining in the ejecta, directly influencing the detectability of predicted 511-keV gamma rays. However, discrepancies between observed and predicted 18F abundances highlight uncertainties in the reaction rates, primarily due to unknown properties of resonances in the compound nucleus 19Ne. In Type I X-ray bursts, the 15O(alpha,gamma)19Ne reaction is instrumental to the breakout of the hot CNO cycle and has been predicted to have considerable impact on energy generation and recurrence times of these phenomena.

To investigate the properties of 19Ne, an indirect experimental approach has been employed utilizing the Super Enge Split-Pole Spectrograph and its associate detector systems at Florida State University to measure the spin-parities, alpha branching ratios, and proton branching ratios of excited states in 19Ne with the 19F(3He,t)19Ne reaction. Significant results include the identification of six near- and sub-proton threshold s-wave resonances which are predicted to have the most impact on the 18F(p,alpha)15O reaction rate. The included S-factor and reaction rate calculations using the 19Ne properties determined in this work show that our findings have significant impact on the reaction rate.

Date

4-1-2025

Committee Chair

Deibel, Catherine

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