Experimental (n,$\gamma$) cross sections of the p-process nuclei $^{74}$Se and $^{84}$Sr

TL;DR

This study reports experimental neutron capture cross sections for p-process nuclei $^{74}$Se and $^{84}$Sr, providing crucial data to constrain theoretical models of nucleosynthesis beyond iron.

Contribution

It provides the first experimental (n,γ) cross sections for $^{74}$Se and $^{84}$Sr, aiding in the calibration of p-process reaction models.

Findings

Measured cross sections for $^{74}$Se and $^{84}$Sr.

Extrapolated Maxwellian averaged cross sections at 30 keV.

Partial cross section to $^{85}$Sr isomer state.

Abstract

The nucleosynthesis of elements beyond iron is dominated by the s and r processes. However, a small amount of stable isotopes on the proton-rich side cannot be made by neutron capture and are thought to be produced by photodisintegration reactions on existing seed nuclei in the so-called "p process". So far most of the p-process reactions are not yet accessible by experimental techniques and have to be inferred from statistical Hauser-Feshbach model calculations. The parametrization of these models has to be constrained by measurements on stable proton-rich nuclei. A series of (n,$\gamma$) activation measurements, related by detailed balance to the respective photodisintegrations, were carried out at the Karlsruhe Van de Graaff accelerator using the $^7$Li(p,n)$^7$Be source for simulating a Maxwellian neutron distribution of kT= 25 keV. First results for the experimental (n,$\gamma$) cross sections of the light p nuclei $^{74}$Se and $^{84}$Sr are reported. These experimental values were used for an extrapolation to the Maxwellian averaged cross section at 30 keV, $<\sigma>_{30}$, yielding 271$\pm$15 mb for $^{74}$Se, and 300$\pm$17 mb for the total capture cross section of $^{84}$Sr. The partial cross section to the isomer in $^{85}$Sr was found to be 190$\pm$10 mb.