Experiments on Parity Non-Conservation in Nuclear Forces in ¹⁸⁰Hf, ¹⁵⁹Tb, ²⁰³Tl-203 and ¹⁸¹Ta

Citation

Lipson, Edward David (1971) Experiments on Parity Non-Conservation in Nuclear Forces in ¹⁸⁰Hf, ¹⁵⁹Tb, ²⁰³Tl-203 and ¹⁸¹Ta. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/NQ36-P768. https://resolver.caltech.edu/CaltechTHESIS:06082018-121644195

Abstract

Weak interaction theories of the "current-current” form predict a weak parity-non-conserving force between nucleons. One manifestation of such a force is the net circular polarization of γ rays from unoriented nuclei. We have measured the circular polarization for four favorable nuclear γ transitions obtaining

¹⁸⁰Hf 501 keV γ: p_γ = (-23 ± 6) x 10^-4
159Tb 363 keV γ: p_γ = (-1 ± 5) x 10 ^-4
203Tl 279 keV γ: P_γ = (-0.04 ± 0.10) x 10^-4
181Ta 482 keV γ: p_γ = (-0.031 ± 0.025) x 10 ^-4

The measurements were performed with a forward-scattering rapidly reversing Compton polarimeter and a phase-sensitive detection system. The analyzing efficiency of the Compton polarimeter, including effects of multiple scattering, was determined by Monte Carlo calculations. It was necessary in most experiments to apply corrections for polarized bremsstrahlung associated with β decays. Calculations of bremsstrahlung effects were verified by experiments on ¹⁹⁸ Au and ¹⁷⁷Lu. The residual asymmetry of the polarimeter itself was determined by contro1 experiments on¹⁰³Ru.

The values of P_γ obtained are compared with related experiments and discussed in the framework of nuclear and weak-interaction theories.

Thesis Files