Abstract :
Our current knowledge of the nucleosynthesis of natureʹs rarest naturally occurring isotope 180Tam is reviewed. Production in the s-process seems possible via a weak branch of thermally β-unstable 179Hf with subsequent neutron capture on the radioactive 179Ta isotope. The effective life time of the long-lived isomer is strongly affected under s-process conditions by thermal coupling to the short-lived ground state through intermediate states. Nevertheless, based on the present knowledge of the relevant nuclear quantities, quantities, close to 100% of the solar abundance can be produced in dynamical s-process models. On the other hand, p-process simulations seem to be able to explain all of the solar abundance. Furthermore, recent improved studies of the ν-process also predict considerable contributions where - contrary to earlier work - the charged current reaction 180Hf(ν, e−) rather than the neutral current reaction 181Ta(ν, ν′n) is most important.
