Measurement of the $^{70}$Ge($n,\gamma$) cross section up to 300~keV at the CERN n_TOF facility

TL;DR

This study measured the neutron capture cross section of $^{70}$Ge up to 300 keV at CERN's n_TOF facility, providing data crucial for understanding nucleosynthesis in massive stars and comparing well with previous measurements and models.

Contribution

It provides new experimental neutron capture data on $^{70}$Ge up to 300 keV, improving the understanding of s-process nucleosynthesis and validating stellar models.

Findings

Resonance capture kernels determined up to 40 keV.

Average cross sections calculated from 5 to 100 keV.

Good agreement with previous data and models.

Abstract

Neutron capture data on intermediate mass nuclei are of key importance to nucleosynthesis in the weak component of the slow neutron capture processes, which occurs in massive stars. The ($n,\gamma$) cross section on $^{70}$Ge, which is mainly produced in the $s$~process, was measured at the neutron time-of-flight facility n_TOF at CERN. Resonance capture kernels were determined up to 40~keV neutron energy, and average cross sections up to 300~keV. Stellar cross sections were calculated from $kT=5$~keV to $kT=100$ keV and are in very good agreement with a previous measurement by Walter and Beer (1985), and recent evaluations. Average cross sections are in agreement with Walter and Beer (1985) over most of the neutron energy range covered, while being systematically smaller for neutron energies above 150~keV. We have calculated isotopic abundances produced in $s$-process environments in a 25 solar mass star for two initial metallicities (below solar, and close to solar). While the low metallicity model reproduces best the solar system germanium isotopic abundances the close to solar model shows a good global match to solar system abundances between mass numbers A=60-80.