Measurement of parity admixtures in nuclear forces in180Hf,181Ta and203Tl

The parity mixing in nuclear states was studied by measuring the circular polarizationP of the γ-radiation emitted from unpolarized nuclei. The analyzer was a “radial transmission magnet” of high symmetry. With 4 NaI scintillation counters and the current integration method 4 independent results were obtained simultaneously. The polarimeter efficiency was determined via the Quadratic Compton effect. Studies of the polarized bremsstrahlung with¹⁷⁰Tm,¹⁷⁷Lu and¹⁹⁸Au sources served as tests for the calculated corrections due to the bremsstrahlung effect. Our results for the circular polarization are:P=?(2.0±0.4) · 10^?3 for the 501 keV transition in¹⁸⁰Hf,p=+(1±4) · 10^?6 for the 482 keV transition in¹⁸¹Ta andP=+(1±7) · 10^?6 for the 279 keV transition in²⁰³Tl. Thus, in the case of¹⁸⁰Hf, the existence of the parity mixing in nuclear states was confirmed.