22Mg

22Mg, or magnesium-22, is a proton-rich radioactive isotope of magnesium with Z=12 and A=22. It lies far from beta stability in the sd-shell region near the proton drip line. The nucleus is unstable and decays predominantly by positron emission to 22Na, with a half-life of about 3.86 seconds. The daughter, 22Na, is itself radioactive with a half-life of 2.6 years.

22Mg is not found in nature and is produced in laboratories by radioactive ion-beam techniques. It can be generated in projectile fragmentation or in fusion-evaporation reactions starting from heavier nuclei. Its short existence and proximity to the proton drip line make it a challenging subject for experimental studies.

In nuclear physics and astrophysics, 22Mg provides a testing ground for models of proton-rich sd-shell nuclei and for studying isospin symmetry. It contributes to understanding reaction rates and pathways in explosive hydrogen burning environments, where proton-capture reactions involving 22Mg may affect nucleosynthesis in novae and X-ray bursts. Ongoing measurements of its beta-decay strength and energy levels help constrain theoretical calculations of proton-rich nuclear structure and inform rp-process models.