First determination of ß -delayed multiple neutron emission beyond A=100 through direct neutron measurement: the P2n value of Sb 136

Background: s-delayed multiple neutron emission has been observed for some nuclei with A=100, being the 100Rb the heaviest s2n emitter measured to date. So far, only 25P2n values have been determined for the ˜300 nuclei that may decay in this way. Accordingly, it is of interest to measure P2n values for the other possible multiple neutron emitters throughout the chart of the nuclides. It is of particular interest to make such a measurement for nuclei with A>100 to test the predictions of theoretical models and simulation tools for the decays of heavy nuclei in the region of very neutron-rich nuclei. In addition, the decay properties of these nuclei are fundamental for the understanding of astrophysical nucleosynthesis processes, such as the r-process, and safety inputs for nuclear reactors.