β-delayed fission and α decay of 178Tl

A detailed nuclear-decay spectroscopy study of the neutron-deficient isotope Tl-178 has been performed using the highly selective Resonance Ionization Laser Ion Source and ISOLDE mass separator (CERN), which allowed a unique isobarically pure beam of Tl-178 to be produced. The first identification of the beta-delayed fission of this isotope was made and its probability P-beta DF(Tl-178) = 0.15(6)% was determined. An asymmetric fission fragment mass distribution of the daughter isotope Hg-178 (populated by the beta decay of Tl-178) was deduced based on the measured fission fragment energies. The fine-structure alpha-decay pattern of Tl-178 allowed the low-energy states in the daughter nucleus Au-174 to be studied.