Date of Award

8-2010

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Physics

Advisor

Meyer, Bradley S

Committee Member

King , Jeremy R

Committee Member

Leising , Mark D

Committee Member

Sosolik , Chad E

Abstract

In this dissertation I analyze internal transitions in nuclei and their potential effects on s-process branching and on accelerated β-decay in cosmochemical samples. To accomplish my analysis, I have constructed a number of computational tools, which I have publicly released or make available through this thesis. I apply my analysis to the question of s-process branching at 186Re and study the implications for the osmium isotopes in mainstream presolar SiC grains. My essential conclusion is that the problem of the large neutron flux inferred from the SiC osmium isotopic abundances cannot be solved by branching through an out-of-equilibrium isomer of 186Re. I also consider the possibility of accelerated β-decay by 176Lu. Measurements of 176Hf excesses in bulk meteorite samples lead to a 4% over-estimate of the age of the solar system when compared to Pb-Pb dating. I confirm that excitation of 176Lu in rocky matter may lead to accelerated -decay due to the existence of a short-lived metastable state at 123 keV. I conclude that enhanced β-decay of 176Lu is a possible and plausible explanation for the age discrepancy observed between various dating methods. Finally I provide a short list of possible s-process branchings which may benefit from similar treatments to that of 186Re, and in the appendices I present some related projects that I have also carried out.

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