The detailed analysis of the $\beta$-delayed fission data of ${}^{180}$Tl is presented. The experiment was performed by producing a pure beam of ${}^{180}$Tl by means of highly selective resonance laser ionization followed by mass separation with the ISOLDE (CERN, Geneva) isotope separator. A surprising asymmetric mass distribution of fission fragments from ${}^{180}$Hg, the daughter of ${}^{180}$Tl $\beta$ decays, was observed. Here, the energy calibration of the silicon detectors, which is crucial for a proper determination of the fission fragments’ energy and mass split, is presented and the total kinetic energy and its dependence on the mass split ratio is discussed. A more precise $\beta$-delayed fission probability $P_{\beta \text{DF}}{(}^{180}\text{Tl})=3.2\left(2\right)\times {10}^{-3}\%$ was deduced.

• Received 14 August 2012

DOI:https://doi.org/10.1103/PhysRevC.88.044321