Radiative neutron capture reaction rates for r-process nucleosynthesis

TL;DR

This paper investigates radiative neutron capture reaction rates near the r-process peak, highlighting uncertainties and the impact of low-energy enhancements on reaction rates crucial for understanding element synthesis in stars.

Contribution

It provides new calculations of (n,γ) cross sections and reaction rates around the r-process peak, emphasizing the effects of low-energy enhancements and uncertainties for neutron-rich nuclei.

Findings

Low-energy enhancements significantly increase reaction rates.

Uncertainties remain large for neutron-rich nuclei.

Reaction rates are critical for modeling r-process nucleosynthesis.

Abstract

About half of the elements beyond iron are synthesized in stars by rapid-neutron capture process (r-process). The stellar environment provides very high neutron flux in a short time ($\sim$ seconds) which is conducive for the creation of progressively neutron-rich nuclei till the waiting point is reached after which no further neutron capture reactions proceed. At this point such extremely neutron-rich nuclei become stable via $\beta^-$ decay. A detailed understanding of the r-process remains illusive. In the present work, we explore the radiative neutron-capture (n,$\gamma$) cross sections and reaction rates around the r-process peak near mass number eighty. The inherent uncertainties remain large in some cases, particularly in case of neutron-rich nuclei. When the low-energy enhancement exists, it results in significant increase in the reaction rate for neutron-capture.