Background: About 50% of heavy elements are produced by the slow neutron capture process ($s$ process) in stars. The element gallium is mostly produced during the weak $s$ process in massive stars.

Purpose: Our activation at $k_{\mathrm{B}}T\approx 25$ keV is the first experiment in a series of activation and time-of-flight measurements on ${}^{69}\mathrm{Ga}$ and ${}^{71}\mathrm{Ga}$ relevant for astrophysics.

Methods: We activated ${}^{69}\mathrm{Ga}$ and ${}^{71}\mathrm{Ga}$ with a neutron distribution that corresponds to a quasistellar distribution with $k_{\mathrm{B}}T=25\mathrm{keV}$ at the Joint Research Centre (JRC), Geel, Belgium. Protons were provided by an electrostatic Van de Graaff accelerator to produce neutrons via the reaction ${}^7\mathrm{Li}(\mathrm{p},\mathrm{n})$. The produced activity was measured via the $\gamma$ emission by the decaying product nuclei by high-purity germanium detectors.

Results: We provide spectrum-averaged cross sections (SACS) and ratios of the cross sections ${\sigma }_{\text{Ga}}/{\sigma }_{\text{Au}}$ for the neutron spectrum of the activation. We obtain values of ${\sigma }_{69\mathrm{Ga},\mathrm{SACS}}=(186\pm 12)\mathrm{mb}$ and ${\sigma }_{71\mathrm{Ga},\mathrm{SACS}}=(112\pm 7)\mathrm{mb}$, and cross-section ratios of ${\sigma }_{\text{69Ga}}/{\sigma }_{\text{Au}}=0.29\pm 0.02$ and ${\sigma }_{\text{71Ga}}/{\sigma }_{\text{Au}}=0.17\pm 0.01$.

Conclusions: Our data disagree with the available evaluated data provided by KADoNiS v0.3, our cross-section ratio is about 20% higher for ${}^{69}\mathrm{Ga}$ and about 20% lower for ${}^{71}\mathrm{Ga}$.

• Received 8 September 2020
• Accepted 19 January 2021

DOI:https://doi.org/10.1103/PhysRevC.103.025802

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Published by the American Physical Society