PARITY MIXING IN 482 KEV STATE IN 181TA

A search has been made for a parity-violating component in the 482 keV level of 181Ta by measuring the degree of circular polarization of the ground state transition. Two Compton transmission analysers were used. The design of the experiment required extreme care because of the small degree of polarization expected, i.e. Pγ ≈ 10-4, and the low efficiency of the Compton analysers. The minimization or elimination of possible causes of a false effect is discussed; control experiments with 60Co and 181Hf sources were used to evaluate any residual asymmetry in the measuring system. Considerable care was taken in the analysis of the data especially as regards the removal of trend effects. A careful investigation of the various sources of systematic error was made; the only significant one found was due to bremsstrahlung. The results obtained were Pγ = -(0.8plusmn;1.4)× 10-4 (analyser efficiency 0.6%), Pγ = -(0.9plusmn;0.6)× 10-4 (analyser efficiency 1.6%). The second result is significantly larger than the calculated effect due to bremsstrahlung (Pγ = -1.6×10-5). It is consistent with the theoretical estimates, which lie in the range Pγ = -(0.4 to 2.7)×10-4. © 1969.