nuclear isomer
Noun
Meaning
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
Synonyms
Examples
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.
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.
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.
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.
Its short-lived gamma ray -emitting nuclear isomer — technetium-99m —is used in nuclear medicine for a wide variety of diagnostic tests.
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.