An "'isomeric transition "'is a radioactive decay process that involves emission of a gamma ray from an atom where the nucleus is in an excited metastable state, referred to in its excited state, as a nuclear isomer.
12.
The process of isomeric transition ( that is, the gamma decay of nuclear isomers ), is therefore similar to any gamma emission from any excited nuclear state, but differs in that it involves excited metastable states of nuclei with longer half lives.
13.
However, 1973 work also showed that the 250 Fm recoil could have also easily been produced from the isomeric transition of 250m Fm ( half-life 1.8 s ) which could also have been formed in the reaction at the energy used.
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They are not observed due to strong but not absolute suppression, by spin-parity selection rules ( for beta decays and isomeric transitions ) or by the thickness of the potential barrier ( for alpha and cluster decays and spontaneous fission ) .-- ->
15.
Sometimes, the gamma decay from a metastable state is given the special name of an isomeric transition, but save for the long-lived nature of the meta-stable parent nuclear isomer, this process resembles shorter-lived gamma decays in all external aspects.
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Gamma decay as a separate phenomenon, with its own half-life ( now termed isomeric transition ), was found in natural radioactivity to be a result of the gamma decay of excited metastable nuclear isomers, which were in turn created from other types of decay.
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Gold's most stable isomer is with a half-life of 2.27 days . Gold's least stable isomer is with a half-life of only 7 ns . has three decay paths : ? + decay, isomeric transition, and alpha decay.
18.
Natural tantalum consists of two isotopes : 180m Ta ( 0.012 % ) and 181 Ta ( 99.988 % ) . 181 Ta is a stable isotope . 180m Ta ( " m " denotes a metastable state ) is predicted to decay in three ways : isomeric transition to the ground state of 180 Ta, beta decay to 180 Hf.
19.
Multiple excitation states have been observed for 80 Y and 97 Y . While most of yttrium's isomers are expected to be less stable than their ground state, 78m Y, 84m Y, 85m Y, 96m Y, 98m1 Y, 100m Y, and 102m Y have longer half-lives than their ground states, as these isomers decay by beta decay rather than isomeric transition.
