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

TL;DR

This paper uses advanced nuclear models to reduce uncertainties in predicting the neutron drip line and r-process paths, crucial for understanding heavy element formation in astrophysics.

Contribution

It demonstrates that the main source of variation in predictions is the uncertainty in nuclear matter symmetry energy, and constrains this to improve predictions of the nuclear landscape.

Findings

More precise neutron drip line predictions

Refined r-process path locations

Enhanced understanding of heavy neutron-rich nuclei

Abstract

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 similar proton drip line, their predictions for 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. Using microscopic density functional theory with a representative set of non-relativistic and relativistic interactions, we demonstrate for the first time that this variation is mainly due to the uncertainty of nuclear matter symmetry energy $E_{\rm{sym}}(\rho_{\rm{sc}})$ at the subsaturation cross density $\rho_{\rm{sc}}=0.11/0.16\times\rho_0$ ($\rho_0$ is saturation density), which reflects the symmetry energy of heavy nuclei. Using the recent accurate constraint on $E_{\rm{sym}}(\rho_{\rm{sc}})$ 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.