Which process synthesizes heavy elements like gold and uranium during or after a CCSN explosion?

Rapid neutron capture (r-process)

While elements up to iron are built up in the stable burning stages leading to core collapse, the synthesis of elements heavier than iron requires environments characterized by extreme temperatures and very high neutron densities, conditions met during the explosion phase itself or potentially during neutron star mergers. This creation mechanism is termed the rapid neutron capture process, or the r-process. During the immense compression, shock propagation, and ensuing aftermath of the CCSN, atomic nuclei are flooded with neutrons faster than they can decay. This allows for the quick addition of multiple neutrons to seed nuclei, resulting in the formation of very heavy, neutron-rich elements such as gold, platinum, and uranium. These newly forged heavy elements are then dispersed throughout the interstellar medium when the supernova ejects the stellar material, enriching subsequent generations of stars and planetary systems.