neutronpoor

Neutron-poor, or neutron-deficient, describes atomic nuclei whose neutron-to-proton ratio is smaller than that of the more common, stable isotopes of the same element. In nuclear physics this term is usually applied to isotopes with N < Z or with a notably low N/Z compared with stable isotopes. Such nuclei lie toward the proton-rich side of the nuclear chart and often approach the proton drip line, where adding more protons would make the nucleus unbound.

Production and decay processes: Neutron-poor isotopes are typically produced in fusion-evaporation reactions, in projectile fragmentation of heavier nuclei, or in secondary beams at radioactive-beam facilities. They tend to be highly unstable and decay toward stability, principally by beta-plus decay (positron emission) or electron capture, and in some cases by alpha decay or other decay modes. Their half-lives can range from milliseconds to seconds or longer for isotopes nearer stability.

Scientific significance: Studying neutron-poor nuclei tests and informs nuclear models, including shell structure, deformation, and the evolution of magic numbers far from stability. These isotopes help map the limits of nuclear binding and clarify the properties of nuclei near the proton drip line. Experimental methods include gamma-ray spectroscopy, mass measurements with Penning traps, and reaction studies using recoil separators and storage rings.

Astrophysical relevance: Proton-rich nuclei participate in nucleosynthesis pathways such as the rapid proton capture process (rp-process) in explosive hydrogen-burning environments like novae and accreting neutron stars. Properties of neutron-poor isotopes influence reaction rates and element production in these environments, shaping our understanding of chemical evolution in the universe.