Isotopically, 14Ĭonstitutes a negligible part but, since it is radioactive with a half-life of 5.70(3) ×10 3 years, it is radiometrically detectable. Is produced by thermal neutrons from cosmic radiation in the upper atmosphere, and is transported down to earth to be absorbed by living biological material. 12Īre stable, occurring in a natural proportion of approximately 93:1. There are three naturally occurring isotopes of carbon: 12, 13, and 14. Main articles: Carbon-12, Carbon-13, and Carbon-14 Among the many molecules used in this context are the radioligands [ 11 It is produced from nitrogen in a cyclotron by the reactionĬarbon-11 is commonly used as a radioisotope for the radioactive labeling of molecules in positron emission tomography. This decay mainly occurs due to positron emission, with around 0.19–0.23% of decays instead occurring by electron capture. Is a radioactive isotope of carbon that decays to boron-11.
^ Ratio of 12C to 13C used to measure biological productivity in ancient times and differing types of photosynthesis.
^ The unified atomic mass unit is defined as 1/12 of the mass of an unbound atom of carbon-12 in its ground state.^ a b c d e Decay mode shown is energetically allowed, but has not been experimentally observed to occur in this nuclide.^ Used for labeling molecules in PET scans.^ Immediately decays by proton emission to 4.^ Subsequently decays by double proton emission to 4.^ # – Values marked # are not purely derived from experimental data, but at least partly from trends of neighboring nuclides (TNN).^ ( ) spin value – Indicates spin with weak assignment arguments.^ Bold symbol as daughter – Daughter product is stable.^ ( ) – Uncertainty (1 σ) is given in concise form in parentheses after the corresponding last digits.Light isotopes tend to decay into isotopes of boron and heavy ones tend to decay into isotopes of nitrogen. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. The most stable artificial radioisotope is 11 This is also the only carbon radioisotope found in nature, as trace quantities are formed cosmogenically by the reaction 14 Carbon ( 6C) has 15 known isotopes, from 8Īre stable.
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