rProzessNukleosynthese

rProzessNukleosynthese, also known as the rapid neutron capture process or r‑process, is a nucleosynthetic pathway responsible for producing roughly half of the elements heavier than iron in the Universe. It operates in environments with extremely high neutron densities, typically exceeding 10^20 neutrons per cubic centimetre, and short timescales on the order of seconds or less. Under such conditions a seed nucleus rapidly captures neutrons before β‑decay can occur, driving the material far from the valley of stability toward very neutron‑rich isotopes. Subsequent β‑decays toward lower neutron number rebuild the element chain, ultimately yielding stable isotopes observed in nature.

The r‑process was first proposed in the 1950s by Otto Struve and later formalized by Burbidge, Burbidge, Fowler, and Hoyle in their classic 1957 paper on nucleosynthesis. It explains the abundance peaks seen around mass numbers A≈80, 130, and 195 in the solar system and is considered the primary source of heavy elements such as gold, platinum, and europium. The leading candidate astrophysical sites are core‑collapse supernovae, where neutrino‑driven winds might provide the necessary neutron flux, and compact binary neutron‑star mergers, which recently received observational evidence from gravitational‑wave and kilonova detections, notably GW170817. Other proposed sites include collapsars and magneto‑rotational supernovae.

Key nuclear physics inputs include neutron‑capture cross sections, fission barriers, and β‑decay rates for hundreds of short‑lived isotopes, data that are still incomplete and require advanced radioactive‑beam facilities. The r‑process remains an active area of research at the intersection of nuclear physics, astrophysics, and observational astronomy, with new insights expected as both theoretical models and experimental capabilities improve.