Positioning the neutron drip line and the r-process paths in the nuclear landscape

Exploring nucleon drip lines and astrophysical rapid neutron capture process (r-process) paths in the nuclear landscape is extremely challenging in nuclear physics and astrophysics. While various models predict a similar proton drip line, their predictions for the neutron drip line and the r-process paths involving heavy neutron-rich nuclei exhibit a significant variation which hampers our accurate understanding of the r-process nucleosynthesis mechanism. By using microscopic density functional theory with a representative set of nonrelativistic and relativistic interactions, we demonstrate for the first time that this variation is mainly due to the uncertainty of nuclear matter symmetry energy Esym(ρsc) at the subsaturation cross density ρsc=0.11/0.16×ρ₀ (ρ₀ is saturation density), which reflects the symmetry energy of heavy nuclei. By using the recent accurate constraint on Esym(ρsc) from the binding-energy difference of heavy-isotope pairs, we obtain quite precise predictions for the location of the neutron drip line, the r-process paths, and the number of bound nuclei in the nuclear landscape. Our results have important implications on extrapolating the properties of unknown neutron-rich rare isotopes from the data on known nuclei.