Temperature effects on neutron-capture cross sections and rates through electric dipole transitions in hot nuclei

The temperature evolution of electric dipole transition strengths of Sn isotopes is studied using self-consistent quasiparticle random phase approximation (QRPA) and finite-temperature RPA models based on a relativistic density functional. For tin isotopes lighter than Sn-132, temperature only shows its effect at high values of 2 MeV, while for neutron-rich tin isotopes heavier than Sn-132, the low-lying strength distributions get fragmented and spread to the lower-energy region already at temperature of 1 MeV. Using these electric dipole transition strengths as inputs for the TALYS code, the temperature effects on (n, gamma) cross sections are studied. For tin isotopes lighter than Sn-132, temperature causes an enhancement of neutron-capture cross section at high temperatures of 2 MeV, while for neutron-rich tin isotopes heavier than Sn-132, the cross section is largely enhanced already at temperature T = 1.0 MeV, and the bump of cross section caused by the pygmy dipole resonance also becomes broader. The change in neutron-capture rate can be as large as 70% for Sn-136, considering the temperature effects on electric dipole transition strength in the final compound nucleus with a temperature of 0.86 MeV (corresponding to T = 10 GK in the astrophysical environment). The change is around 20% for tin isotopes lighter than Sn-132 and above 40% for those heavier than Sn-132.

Automated summary

This study investigates the temperature evolution of electric dipole transition strengths of tin isotopes using self-consistent quasiparticle random phase approximation (QRPA) and finite-temperature RPA models based on a relativistic density functional. It was found that for lighter tin isotopes, temperature mainly affects at high temperatures, while for neutron-rich tin isotopes, the low-lying strength distributions become fragmented at lower temperatures. Additionally, the temperature effects on (n, gamma) cross sections were studied, showing significant enhancements for both light and neutron-rich tin isotopes.