Low-lying dipole response in the Relativistic Quasiparticle Time Blocking Approximation and its influence on neutron capture cross sections

TL;DR

This paper uses the RQTBA method to compute dipole strength distributions in nickel and tin isotopes, revealing enhanced low-energy dipole strength that impacts neutron capture rates crucial for r-process nucleosynthesis.

Contribution

It introduces the application of RQTBA to calculate dipole strengths in neutron-rich isotopes and assesses their influence on astrophysical neutron capture rates.

Findings

Enhanced dipole strength near neutron threshold in neutron-rich nuclei

Neutron capture rates are sensitive to low-lying dipole strength details

Good agreement with experimental data for tin isotopes

Abstract

We have computed dipole strength distributions for nickel and tin isotopes within the Relativistic Quasiparticle Time Blocking approximation (RQTBA). These calculations provide a good description of data, including the neutron-rich tin isotopes $^{130,132}$Sn. The resulting dipole strengths have been implemented in Hauser-Feshbach calculations of astrophysical neutron capture rates relevant for r-process nucleosynthesis studies. The RQTBA calculations show the presence of enhanced dipole strength at energies around the neutron threshold for neutron rich nuclei. The computed neutron capture rates are sensitive to the fine structure of the low lying dipole strength, which emphasizes the importance of a reliable knowledge of this excitation mode.