Parity Non-Conservation Observed in Nuclear γ-Decay of 180mHf

This paper presents results of experiment which studied (using the Nuclear-Orientation technique) the γ - decay of isomeric 180mHf. The described experiment used the newly developed mass-separated 180mHf beam at ISOLDE, CERN which was implanted into an iron foil polarized at millikelvin temperatures. The observed irregular admixture of E2 to M2/E3 multipolarity in 501 keV 8- → 6+ γ transition was the clear experimental evidence for parity mixing in nuclear states. The temperature dependence of the forward-backward asymmetry of the angular distribution has been measured over extended range of temperatures (and therefore nuclear polarizations), proving a parity mixing of the 8- and 8+ nuclear levels. The value found for the E2/M2 mixing ratio ε = -0.032(2) of this transition is in close agreement with averaged value of all previously published results ε = -0.030(2). (author)