β-delayed fission of 180Tl

The detailed analysis of the beta-delayed fission data of Tl-180 is presented. The experiment was performed by producing a pure beam of Tl-180 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 Hg-180, the daughter of Tl-180 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 DF(Tl-180) = 3.2(2) x 10(-3)% was deduced.