$β$-delayed fission of $^{180}$Tl

The detailed analysis of the β-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 $β$ 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 $β$-delayed fission probability $P_{β\textrm{DF}}(^{180}\textrm{Tl})=3.2(2)×10^{−3}%$ was deduced.