Noun
English Wikipedia has an article on:nuclear isomerWikipedia
nuclear isomer (plural nuclear isomers)
(physics) Any of two or more atomic nuclei with the same mass number and atomic number but with different radioactive properties
A nuclear isomer may also be called a " meta -state", meaning the system has more internal energy than the " ground state " (the state with the lowest possible internal energy), making the former likely to decay into the latter. Source: Internet
All "stable" isotopes (stable by observation, not theory) are the ground states of nuclei, with the exception of tantalum-180m, which is a nuclear isomer or excited state. Source: Internet
Cells with colored borders (note the three bottom cells in the color legend at right) denote the half-life of the most stable nuclear isomer state. Source: Internet
However, radioactivity of this nuclear isomer has never been observed, and only a lower limit on its half life of 2.0 × 10 16 years has been set. citation The ground state of 180 Ta has a half life of only 8 hours. Source: Internet
Its short-lived gamma ray -emitting nuclear isomer — technetium-99m —is used in nuclear medicine for a wide variety of diagnostic tests. Source: Internet
The ground state of this particular nucleus, Ta-180, is radioactive with a comparatively short half-life of 8 hours; in contrast, the decay of the excited nuclear isomer is extremely strongly forbidden by spin-parity selection rules. Source: Internet