Rprosessin

rprosessin, commonly known in English as the rapid neutron‑capture process (r-process), is a mode of nucleosynthesis responsible for forming roughly half of the elements heavier than iron. In this process, atomic nuclei rapidly capture neutrons in environments with extremely high neutron flux, pushing nuclei far from stability before beta decays can occur.

The r-process requires conditions with intense neutron densities and high temperatures. Potential astrophysical sites include core‑collapse supernovae and neutron‑star mergers, with accumulating observational support from kilonovae associated with gravitational wave events such as GW170817. The exact sites remain active areas of research, and different environments may contribute to the observed abundance of heavy elements.

Mechanistically, the r-process proceeds faster than most beta decays, so nuclei move along a path of highly neutron‑rich isotopes toward the neutron drip line. Once the neutron flux subsides, rapid beta decays convert neutrons into protons, producing stable or long‑lived heavy nuclei. The final abundances depend on nuclear properties such as masses, beta‑decay half-lives, and neutron‑capture rates, all of which are uncertain for extremely neutron‑rich species.

Evidence for the r-process includes the solar system’s heavy-element abundance pattern, which is reproduced well by a scaled r‑process contribution, and observations of metal‑poor stars showing enhanced r‑process elements. Kilonova observations provide direct signatures of r‑process nucleosynthesis in neutron‑rich ejecta.

rprosessin remains central to understanding chemical evolution and the origin of the heaviest elements. Ongoing experiments with rare‑isotope beams and advanced astrophysical modeling aim to resolve remaining uncertainties about sites and nuclear physics that shape its yields.

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