R-process

The r-process is a nucleosynthesis process, occurring in core-collapse supernovae (see also supernova nucleosynthesis) and to a slight extent in nuclear weapon explosions, which is responsible for the creation of approximately half of the neutron-rich atomic nuclei that are heavier than iron. The process entails a succession of rapid neutron captures (hence the name r-process) by heavy seed nuclei, typically 56Fe or other more neutron-rich heavy isotopes. The other predominant mechanism for the production of heavy elements is the s-process, which is nucleosynthesis by means of slow captures of neutrons, primarily occurring in AGB stars. The s process is secondary, meaning that it requires preexisting heavy isotopes as seed nuclei to be converted into other heavy nuclei. Taken together these two processes account for a majority of galactic chemical evolution of elements heavier than iron.