Experiments on parity nonconservation in nuclear Forces. III. Gamma transitions in Hf180, Tb159, Ta181, Tl203, and W182

We have further studied the parity admixtures in nuclear γ transitions by measuring the circular polarization of γ rays from five nuclei with a technique different from that of our work I and II in this series. The experiments 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 Au198 and Lu177. The residual asymmetry of the polarimeter itself was determined by control experiments on Ru103. The values of Pγ obtained were Hf180 501 keV, Pγ=(-23±6)×10-4; Tb159 363 keV, Pγ=(-1±5)×10-4; Tl203 279 keV, Pγ=(-0.04±0.10)×10-4; Ta181 482 keV, Pγ=(-0.031±0.025)×10-4; W182 1189 keV, Pγ=(-0.25±0.40)×10-4. A survey and a discussion of these results is presented.