Iron-55

Iron-55 (⁵⁵Fe) is a radioactive isotope of iron. It is not a naturally occurring isotope, being primarily produced in nuclear reactors and as a byproduct of certain nuclear weapon detonations. It decays via electron capture with a half-life of approximately 2.7 years (977.9 days). This decay results in the emission of characteristic X-rays, primarily manganese K X-rays, which are used in various applications.

The electron capture decay process involves the nucleus capturing an inner shell electron, which converts a proton into a neutron. This results in the formation of manganese-55 (⁵⁵Mn) and the emission of a neutrino and X-rays. The X-rays are produced when other electrons drop into the vacancies created by the captured electron.

Iron-55 finds use as a radioactive tracer in biological and medical research, primarily due to its relatively low energy emissions and manageable half-life. It has also been used in electron capture detectors in gas chromatography. In this application, the emitted X-rays ionize the carrier gas, enabling the detection of compounds with high electron affinity. It's important to note that handling Iron-55 requires appropriate safety precautions due to its radioactivity.