Neutron-capture rates on unstable neutron-rich nuclei
In plain words
As matter cools after an r-process event, the rate at which unstable nuclei absorb extra neutrons shapes the final abundance pattern. These rates cannot be measured directly because the nuclei live too briefly to be made into targets.
Precise statement
Determine $(n, \gamma)$ rates at $T\ \text{about}\ 1e9\,\mathrm{K}$ for nuclei 10 to 20 neutrons beyond stability to within a factor of 2 (model predictions differ by up to two orders of magnitude far from stability), using indirect methods: the beta-Oslo method (gamma strength and level density from beta-decay feeding), surrogate reactions, and $(d, p)$ on radioactive beams. Answer: rates for the nuclei with largest abundance sensitivity and validated statistical-model inputs.
What would settle it
Beta-Oslo and surrogate measurements at FRIB covering the sensitivity-ranked nuclei, cross-checked against direct measurements where possible.