neutronrijke

Neutronrijke (neutron-rich) describes atomic nuclei that contain more neutrons than protons, i.e., N > Z. These nuclei lie toward the neutron-rich side of the nuclear chart. Most neutron-rich isotopes are unstable and decay toward stability, typically via beta decay. The degree of neutron excess is measured by N/Z or by N−Z; the neutron drip line marks the boundary where adding a neutron yields an unbound system.

Production and study: Neutron-rich nuclei are produced in nuclear reactions such as projectile fragmentation, fission, or spallation, using radioactive ion beam facilities. Examples of laboratories include FRIB (USA), RIBF (Japan), FAIR (Germany), and GANIL (France). Researchers determine masses, beta-decay half-lives, and neutron emission properties with specialized separators and detectors.

Relevance: They are essential for understanding nuclear structure far from stability, the neutron-rich matter equation of state, and astrophysical processes. In particular, many neutron-rich nuclei influence the rapid neutron capture process (r-process) responsible for creating a substantial portion of the elements heavier than iron in extreme environments such as neutron-star mergers and certain supernovae.

Notes: The term is relative; while some neutron-rich isotopes are long-lived, most near the drip line have short half-lives. Ongoing experimental and theoretical work aims to map the neutron-rich regions of the nuclear chart and to refine models of nuclear forces and shell evolution as neutrons dominate the nucleus.