Editing Nuclear isomer (section)

==Decay processes==
An '''isomeric transition''' or '''internal transition'''<!-- NUBASE2020 p20 --> (IT) is the decay of a nuclear isomer to a lower-energy nuclear state. The actual process has two types (modes):<ref name="DavidDarling">{{Cite web |url=http://www.daviddarling.info/encyclopedia/I/isomeric_transition.html |title=isomeric transition |last=Darling |first=David |website=Encyclopedia of Science |access-date=2019-08-16}}</ref><ref name="Gardiner">{{Cite web |url=http://nssc.physics.ucdavis.edu/wp-content/uploads/2016/04/decay_scheme_guide.pdf |title=How to read nuclear decay schemes from the WWW Table of Radioactive Isotopes |last=Gardiner |first=Steven |date=2017-08-12 |website=University of California |access-date=2019-08-16 |archive-date=21 September 2018 |archive-url=https://web.archive.org/web/20180921061211/http://nssc.physics.ucdavis.edu/wp-content/uploads/2016/04/decay_scheme_guide.pdf |url-status=dead }}</ref>
* [[gamma ray|γ (gamma ray)]] emission (emission of a high-energy photon),
* [[internal conversion]] (the energy is used to eject one of the atom's electrons).
Isomers may decay into other elements, though the rate of decay may differ between isomers. For example, <sup>177m</sup>Lu can beta-decay to <sup>177</sup>[[Hafnium|Hf]] with a half-life of 160.4&nbsp;d, or it can undergo isomeric transition to <sup>177</sup>Lu with a half-life of 160.4&nbsp;d, which then beta-decays to <sup>177</sup>Hf with a half-life of 6.68&nbsp;d.<ref name=Litz04 />

The emission of a gamma ray from an excited nuclear state allows the nucleus to lose energy and reach a lower-energy state, sometimes its [[ground state]]. In certain cases, the excited nuclear state following a [[nuclear reaction]] or other type of [[radioactive decay]] can become a [[metastable]] nuclear excited state. Some nuclei are able to stay in this metastable excited state for minutes, hours, days, or occasionally far longer.

The process of isomeric transition is similar to gamma emission from any excited nuclear state, but differs by involving excited metastable states of nuclei with longer half-lives.  As with other excited states, the nucleus can be left in an isomeric state following the emission of an [[alpha particle]], [[beta particle]], or some other type of particle.

The gamma ray may transfer its energy directly to one of the most tightly bound [[electron]]s, causing that electron to be ejected from the atom, a process termed the [[photoelectric effect]]. This should not be confused with the [[internal conversion]] process, in which no gamma-ray photon is produced as an intermediate particle.