PARITY MIXING IN 482 KEV TRANSITION OF 181TA

The parity impurity of the 482 keV gamma transition of 181Ta has been investigated by a measurement of the circular polarization. The polarimeter construction is based on the polarization dependence of the Compton scattering cross section for magnetized iron. A 4π backscattering geometry is applied in order to reach a high circular polarization detection efficiency combined with a large transmission. The scattered radiation is detected simultaneously by six large plastic scintillators, each of which is connected to a fast scaling system. Possible reasons for systematic errors are carefully investigated. Systematic asymmetries of the polarimeter were measured by use of the 497 keV gamma radiation of 103Rh. One does not expect a circular polarization for this radiation. We found for the circular polarization of the 482 keV transition in 181Ta the value Pγ = -(2.8±0.6). 10-5. The error is the standard deviation. Our result is compared with theoretical predictions and previous experiments. © 1969.