Light-Element Reaction Flow and the Conditions for r-Process Nucleosynthesis

We deduce new constraints on the entropy per baryon ($s/k$), dynamical timescale ($tau_{dyn}$), and electron fraction ($Y_{e}$) consistent with heavy element nucleosynthesis in the r-process. We show that the previously neglected reaction flow throu gh the reaction sequence atg (n,$gamma$)Li~ significantly enhances the production of seed nuclei. We analyze the r-process nucleosynthesis in the context of a schematic exponential wi nd model. We show that fewer neutrons per seed nucleus implies that the entropy per baryon required for successful r-process nucleosynthesis must be more than a factor of two higher than previous estimates. This places new constraints on dynamical mo dels for the r-process.