12/15/2023
By Sean Byrne

The Kennedy College of Sciences, Department of Physics and Applied Physics, invites you to attend a master's thesis defense by Sean Byrne on “Constraining the Half-Life of 72Rb."

Candidate Name: Sean Byrne
Defense Date: Wednesday, Dec. 20, 2023
Location: Pinanski 202 , 2nd Floor Pinanski Hall
Thesis Title: Constraining the Half-Life of 72Rb”

Advisor: Andrew Rogers Ph.D., Physics and Applied Physics

Committee Members: Partha Chowdhury, Ph.D., Ofer Cohen, Ph.D., Physics and Applied Physics;

Abstract:
Studies of isotopes at the limits of existence are important for testing nuclear theory and for the role they play in nuclear astrophysics. The proton drip line is one such diffusely defined boundary. Where subtle changes in the nuclear structure can enhance or reduce the relative stability and lifetime of these quantum-mechanical systems. Mid-Mass ( A~70) atomic nuclei at the drip line are particularly interesting as they lie along the N=Z line; enabling tests of mirror symmetry and, since nuclei in this region are highly deformed, features of nuclear shapes can be explored. Understanding properties of these nuclei is crucial for constraining the rapid proton capture (rp) process. Thought to drive type I x-ray bursts that can occur on the surface of accreting neutron stars. In this region, 72Rb was recently observed for the first time, at RIKEN in 2016. It was identified as a so-called “sandbank” since it is more stable than its unbound neighbor, 73Rb, yet exists beyond the proton drip line. This previous discovery experiment was able to provide the first measurement of the half-life, 103(22) ns. This thesis focuses on the analysis of a 2017 experiment conducted at the National Cyclotron Superconducting Laboratory (NSCL) where 72Rb was produced through projectile fragmentation. Similar to the RIKEN measurement, a missing-yield technique was used to determine the relative number of ions that decayed in-flight as they are transported to the experiment’s end-station, thereby enabling a measurement of the half-life. This new measurement provides additional insight that can be used to improve nuclear theory and constrain astrophysical nucleosynthesis calculations, as well as aiding in planning future experiments that propose to directly study the decay of 72Rb.