Recent $\beta $-delayed neutron branching ratios of measurements with heavy nuclei.

The understanding of the nuclear structure of the neutron-rich nuclei and several astrophysical phenomena, such as the r-process, is a challenge that need new experimental values to provide more realistic data inputs in theoretical models. The aim of this study is to achieve new $\beta $-delayed neutron branching ratios, Pn, of very neutron-rich nuclei. Experiments recently performed at the RIB facilities of GSI Darmstadt (Germany) and IGISOL in Jyv\"{a}skyl\"{a} (Finland) allowed to determine Pn values for heavier isotopes than those measured so far with a 4pi neutron detector based on $^{\mathrm{3}}$He counters. At GSI it was possible to measure $\beta $1n emitters for several Hg and Tl isotopes with masses beyond A\textgreater 200 and N\textgreater 126, and at IGISOL the $\beta $2n emitter $^{\mathrm{136}}$Sb, which represents an important leap in terms of mass since the heaviest known were around A\textasciitilde 150 for $\beta $1n and A\textasciitilde 100 for $\beta $2n. Results of P1n and P2n values will be presented, together with the new plans for $\beta $-delayed neutron emitter measurements at RIKEN (Japan). The BRIKEN project aims to measure more than a hundred of $\beta $1n, and many $\beta $2n and $\beta $3n emitters, a lot of them for the first time. These isotopes will be the most neutron-rich species measured so far.