2025ApJ...988..170K

The cross section of the ⁸⁶Kr(α, n)⁸⁹Sr reaction was measured at low energies using the activation technique via the detection of the β^– emission from the residual ⁸⁹Sr nuclei. The theoretical analysis of the measured cross sections shows that the new data can be well described in the statistical model using several recent α-nucleus potentials. The resulting astrophysical reaction rate has small uncertainties between about 15% at higher temperatures and up to a factor of 2 at low temperatures. Using this new reaction rate of the ⁸⁶Kr(α, n)⁸⁹Sr reaction for the nucleosynthesis in neutrino-driven outflows in core-collapse supernovae leads to well-constrained production ratios for the nuclei slightly above krypton (Z = 36) like Sr/Zr, Y/Zr, and Mo/Zr. A comparison to observational ratios in metal-poor stars allows to constrain the astrophysical conditions for this weak r-process.