Overview

This dissertation describes two high-precision measurements concerning isospin symmetry breaking in nuclei. (1) We determined, with unprecedented accuracy and precision, the excitation energy of the lowest T = 2; Jpi = 0+ state in 32S using the 31P(p; gamma) reaction. This excitation energy, together with the ground state mass of 32S, provides the most stringent test of the isobaric multiplet mass equation (IMME) for the A = 32, T = 2 multiplet. We observe a significant disagreement with the IMME and investigate the possibility of isospin mixing with nearby 0+ levels to cause such an effect. In addition, as byproducts of this work, we present a precise determination of the relative gamma-branches and an upper limit on the isospin violating branch from the lowest T = 2 state in 32S. (2) We obtained the superallowed branch for the 0+ → 0 + Fermi decay of 32Ar. This involved precise determinations of the beta-delayed proton and gamma branches. The gamma-ray detection efficiency calibration was done using precisely determined gamma-ray yields from the daughter 32Cl nucleus from another independent measurement using a fast tape-transport system at Texas A&M University. This superallowed branch, along with previously determined half-life and QEC value measurements, provides the ft value for the decay. On comparison with the ft values of nine previously measured T = 1 → T = 1 Fermi transitions, this provides a useful check of calculated isospin breaking corrections, which, in the case of 32Ar, is ≈3 times larger than the nine measured cases. The calculated corrections for nuclear beta decays play an important role in determining V ud, the first element of the CKM matrix.

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