Heterotopic nucleus
The heterotopic nucleus is a metastable nucleus due to the lifting of one or more nucleons. "Metastable" means that the excited state has a half-life of 100 to 1000 times the half-life of the other excited states. That is, the term \u0026 quot; metastable \u0026 quot; refers only to isomers having a half-life of at least 10-9 seconds. Sometimes it has a longer half-life, and can be minutes, hours, or even 1015 years. Sometimes gamma decay in the metastable state is called a heterogeneous nuclear transformation. However, except for the long lifetime of metastable parent nuclear isomers, this process is similar to the gamma decay of shorter lifespan in all other respects.