Using (α, xn) reaction rates and abundance ratios to constrain the weak r-process

Abstract The lighter heavy elements of the first r-process peak, between strontium and silver, can be synthesized in the moderately neutron-rich neutrino–driven ejecta of either core–collapse supernovae or neutron star mergers via the weak r–process. This nucleosynthesis scenario exhibits uncertainties from the absence of experimental data from ( α, xn ) reactions on neutron–rich nuclei, which are currently based on statistical model estimates. We have performed a new impact study to identify the most important ( α, xn ) reactions that can affect the production of the lighter heavy elements under different astrophysical conditions and using new, constrained ( α, xn ) reaction rates based on the Atomki-V2 α OMP. We have identified a list of relevant reactions that affect elemental abundance ratios that can be compared to abundances from metal-poor stars. Our results show how when reducing the nuclear physics uncertainties, we can use abundance ratios to constrain the astrophysical conditions/environment. This will be possible with the planned experiments to measure key ( α, xn ) reaction rates using the SECAR recoil separator at FRIB that will also be briefly discussed.