The study of neutron-rich nuclei production in the region of the closed shell N=126 in the multi-nucleon transfer reaction $^{136}$Xe+$^{208}$Pb
Résumé
The unexplored area of heavy neutron rich nuclei is extremely important for nuclear
astrophysics investigations and, in particular, for the understanding of the r-process of
astrophysical nucleogenesis. For the production of heavy neutron rich nuclei located along the
neutron closed shell N=126 (probably the last "waiting point" in the r-process of nucleosynthesis)
the low-energy multi-nucleon transfer reaction 136Xe+208Pb at Elab=870MeV was explored.
Due to the stabilizing e ect of the closed neutron shells in both nuclei, N=82 and N=126, and
the rather favorable proton transfer from lead to xenon, the light fragments formed in this process
are well bound and the Q-value of the reaction is nearly zero.
Measurements were performed with the PRISMA spectrometer in coincidence with an additional
time-of-flight (ToF) arm on the +20 beam line of the PIAVE-ALPI accelerator in Legnaro, Italy.
The PRISMA spectrometer allows identi cation of the A, Z and velocity of the projectile-like
fragments (PLF), while the second arm gives access to the target-like fragments (TLF).
Details on the experimental setup and preliminary results are reported.