Finding impactful neutron capture isotopes in r-process nucleosynthesis through correlation analyses

Half of the elements in the universe heavier than Iron were synthesized in r-process nucleosynthesis, i.e. when seed nuclei capture several free neutrons successively and emit photons (i.e. (n,gamma) reactions), followed by beta decays to stability. These occur in material ejected from neutron star mergers, magnetorotational supernovae, collapsars, magnetar giant flares, and potentially in other conditions. Nuclear reaction network calculations to obtain the elemental yields in this process requires knowledge of neutron capture reaction rates on thousands of isotopes that are hard to measure experimentally. In this work we find that among the thousands of isotopes only a handful, typically 2-3, isotopes influence the production of each element in various weak r-process astrophysical conditions. These isotopes are usually about 5-7 neutrons off stability and are either directly in the beta decay path of forming the most abundant stable isotope or 1 or 2 isotopes off. These play isotopes are abundantly populated during the (n,g) (g,n) freezeout and are the main pathways to producing the stable isotope. Further, we have developed correlation based impact study where the neutron capture reaction rates are correlated due to optical model potential. With these correlations we show that what can be classified as the most influential isotope for an element's production changes substantially.