Astrophysics of neutron-capture processes involving unstable isotopes and the impact of rate uncertainties

The elements heavier than Fe are mostly made by neutron capture processes. Two well-established regimes, the slow (s) and the rapid (r) process have been well studied. The s process takes place in quiescent stellar burning regimes of low-mass Asymptotic Giant Branch stars as well as in He-core and C burning in massive stars. The r process takes place in the extreme conditions of neutron star mergers and certain supernova- related regimes. Over recent years observational and theoretical developments have revealed the existing of neutron-capture regimes in-between the s and r processes. The intermediate (i) process takes place in convective-reactive He-burning when unprocessed H-rich material is convectively entrained, leading to an intricate nucleosynthesis pathway to neutron release that involves the tight coupling of convective advection and nuclear reactions on time scales of minutes to hours. The resulting neutron-capture reactions involve many radioactive species. I will outline the nuclear data needs for this new frontier of nuclear astrophysics, and how experimental nuclear physics advances will enable validating our integrated three-dimensional simulations of dynamic, convective-reactive nuclear astrophysics in advanced evolutionary stages of stars. A similar yet slightly more extreme n-process regime may exist in explosive He-burning induced by supernova explosions.