Large-scale continuum random-phase approximation predictions of dipole strength for astrophysical applications

摘要

Large-scale calculations of the E1 strength are performed within the random phase approximation (RPA)nbased on the relativistic point-coupling mean field approach in order to derive the radiative neutron capturencross sections for all nuclei of astrophysical interest. While the coupling to the single-particle continuumnis taken into account in an explicit and self-consistent way, additional corrections like the coupling toncomplex configurations and the temperature and deformation effects are included in a phenomenologicalnway to account for a complete description of the nuclear dynamical problem. It is shown that thenresulting E1-strength function based on the PCF1 force is in close agreement with photoabsorption datanas well as the available experimental E1 strength data at low energies. For neutron-rich nuclei, as wellnas light neutron-deficient nuclei, a low-lying so-called pygmy resonance is found systematically in then5–10 MeV region. The corresponding strength can reach 10% of the giant dipole strength in the neutron-richnregion and about 5% in the neutron-deficient region, and is found to be reduced in the vicinity of the shellnclosures. Finally, the neutron capture reaction rates of neutron-rich nuclei is found to be about 2–5 times largernthan those predicted on the basis of the nonrelativistic RPA calculation and about a factor 50 larger than obtainednwith traditional Lorentzian-type approaches.