Measurement of Near-Threshold Proton Branching Ratios in 31S Important for Novae

Author

Sudarsan Balakrishnan, Louisiana State University and Agricultural and Mechanical CollegeFollow

Degree

Doctor of Philosophy (PhD)

Department

Department of Physics and Astronomy

Document Type

Dissertation

Abstract

Classical novae are stellar explosions that contribute to the nucleosynthesis of isotopes on the proton-rich side of the valley of stability up to ⁴⁰Ca. In ONe novae, the incompletely understood reaction rate of ³⁰P(p,γ)³¹S is known to strongly influence the production rate of several stable isotopes such as ³⁰Si, ³¹P, and ^32,33,34S. A precise measurement of this reaction rate has several potential implications towards matching astrophysical observables to the physical composition of the nova site -- the observed elemental abundance ratios of O/S and S/Al have been suggested as useful `thermometers' to gauge the temperature of nova explosions, while the Si/H ratio observed is predicted to be correlated with the degree of mixing between accreted hydrogenic matter and the heavier elements in the white-dwarf surface. In addition, the abundance of ³⁰Si relative to ²⁸Si has been suggested as a potential tracer to distinguish between pre-solar meteoritic grains with ONe nova origins and grains with supernova/solar origins. We used the Super Enge Split-pole spectrograph (SE-SPS) at Florida State University to study levels close to the proton threshold of ³¹S using the ²⁸Si(⁶Li, t)³¹S transfer reaction. The Silicon Array for Branching Ratio Experiments (SABRE) was used to detect protons emitted from unbound states in ³¹S, in coincidence with tritons detected at the focal plane of the SE-SPS. Decay protons from the E_x = 6.636 MeV resonance in ³¹S were observed for the first time. The measured ³¹S level structure, proton-branching ratios and spin-parities were used to determine an updated ³⁰P(p,γ)³¹S reaction rate.

Date

1-4-2023

Recommended Citation

Balakrishnan, Sudarsan, "Measurement of Near-Threshold Proton Branching Ratios in 31S Important for Novae" (2023). LSU Doctoral Dissertations. 6032.
https://repository.lsu.edu/gradschool_dissertations/6032

Committee Chair

Deibel, Catherine M.

DOI

10.31390/gradschool_dissertations.6032