How does rapid-neutron capture differ from slow-neutron capture?

The distinction between rapid-neutron capture (the r-process) and slow-neutron capture (the s-process) lies in the rate at which neutrons are added to a nucleus relative to the rate of beta decay.12

• Slow-neutron capture (s-process): Neutrons are added at a rate that allows an unstable nucleus sufficient time to undergo beta decay before another neutron is captured. This process typically occurs during quiet stages of stellar evolution.1
• Rapid-neutron capture (r-process): Neutrons are added so quickly that unstable nuclei cannot decay before additional neutrons are captured. This continues until a nucleus is produced that will not accept further neutrons, at which point it undergoes beta decay. This process occurs in explosive environments, such as nuclear explosions, where a target is bombarded by a high number of fast neutrons in a fraction of a second.12

While the s-process tends to produce isotopes with relatively more protons, the r-process produces the most neutron-rich isotopes of heavy elements and is responsible for creating naturally radioactive nuclei.1