Enhanced symmetry energy may bear universality of r-process abundances

Abstract

The abundances of about half of the elements heavier than iron are subtly attuned by the rapid neutron capture process or r -process, which is intimately related to the competition between neutron capture, photo-disintegration, and β-decay rates, and ultimately depends on the binding energy of neutron-rich nuclei. The well-known Bethe–Weizs ¨acker semi-empirical mass formula describes the binding energy of ground states –i.e. nuclei with temperatures of T = 0 MeV –with the symmetry energy parameter converging between 23 and 27 MeV for heavy nuclei. We find an unexpected enhancement of the symmetry energy well. The abundances of about half of the elements heavier than iron are subtly attuned by the rapid neutron capture process or r -process, which is intimately related to the competition between neutron capture, photo-disintegration, and β-decay rates, and ultimately depends on the binding energy of neutron-rich nuclei. The well-known Bethe–Weizs ¨acker semi-empirical mass formula describes the binding energy of ground states –i.e. nuclei with temperatures of T = 0 MeV –with the symmetry energy parameter converging between 23 and 27 MeV for heavy nuclei. We find an unexpected enhancement of the symmetry energy well The abundances of about half of the elements heavier than iron are subtly attuned by the rapid neutron capture process or r -process, which is intimately related to the competition between neutron capture, photo-disintegration, and β-decay rates, and ultimately depends on the binding energy of neutron-rich nuclei. The well-known Bethe–Weizs ¨acker semi-empirical mass formula describes the binding energy of ground states –i.e. nuclei with temperatures of T = 0 MeV –with the symmetry energy parameter converging between 23 and 27 MeV for heavy nuclei. We find an unexpected enhancement of the symmetry energy well abo v e the ground state –at higher temperatures of T ≈0.7–1.0 MeV –from the available data of giant dipole resonances built on excited states.