Photoneutron cross sections for Ni isotopes: Toward understanding $(n,\gamma)$ cross sections relevant to the weak s-process nucleosynthesis

TL;DR

This study measures photoneutron cross sections for Ni isotopes to improve understanding of neutron capture processes relevant to weak s-process nucleosynthesis, combining experimental data with theoretical models to refine cross section calculations.

Contribution

The paper provides new experimental photoneutron data for Ni isotopes and integrates it with theoretical models to enhance neutron capture cross section predictions for nucleosynthesis.

Findings

New photoneutron cross sections for Ni isotopes were measured.

The data improved the gamma-ray strength function used in cross section calculations.

Calculated Maxwellian-averaged cross sections inform s-process nucleosynthesis models.

Abstract

Photoneutron cross sections were measured for $^{58}$Ni, $^{60}$Ni, $^{61}$Ni, and $^{64}$Ni at energies between the one-neutron and two-neutron thresholds using quasi-monochromatic $\gamma$-ray beams produced in laser Compton-scattering at the NewSUBARU synchrotron radiation facility. The new photoneutron data are used to extract the $\gamma$-ray strength function above the neutron threshold complementing the information obtained by the Oslo method below the threshold. We discuss radiative neutron capture cross sections and the Maxwellian-averaged cross sections for Ni isotopes including $^{63}$Ni, a branching point nucleus along the weak s-process path. The cross sections are calculated with the experimentally constrained $\gamma$-ray strength functions from the Hartree-Fock-Bogolyubov plus quasi-particle-random phase approximation based on the Gogny D1M interaction for both $E1$ and $M1$ components and supplemented with the $M1$ upbend.