Abstract
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 effect 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 identification 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.
Highlights
The transfer of many nucleons was suggested as a feasible route to synthesize heavy nuclei on the neutron-rich side of the stability line [1],[2],[3], giving rise to a renewed interest in the study of transfer processes
PRISMA is a large-acceptance magnetic spectrometer, operating at Laboratori Nazionali di Legnaro (LNL), designed for identification of reaction products of heavy ion collisions consisting of a Micro Channel Plate detector (MCP), a focusing quadrupole, a dipole magnet, a focal Multiwire Parallel Plate detector
For our present case study, the PRISMA setup had in its implementation a second arm, composed of a CORSET [5] compact Micro Channel Plate (MCP) start detector followed by a position-sensitive stop detector and, a Bragg ionization chamber
Summary
The transfer of many nucleons was suggested as a feasible route to synthesize heavy nuclei on the neutron-rich side of the stability line [1],[2],[3], giving rise to a renewed interest in the study of transfer processes. The low-energy collision of 136Xe with 208Pb was explored. The stabilizing effects of the neutron closed shell N = 82 of 136Xe and N = 126 of 208Pb, together with the specific trend of the Q-values of all possible mass transfer channels [4], make the chosen system a very good candidate. Protons may experience a higher mobility due to of the neutron closed shell in the projectile and target, and the transfer of several protons from Xe to Pb may lead to very neutron-rich nuclides [3]
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