Isotopes of carbon
type of stable carbon atoms
Carbon (6C) has 14 known isotopes, from 8C to 20C as well as 22C, of which only 12C and 13C are stable. The longest-lived radioisotope is 14C, with a half-life of 5700 years. This is also the only carbon radioisotope found in nature, as trace quantities are formed cosmogenically by the reaction 14N + n → 14C + 1H. The most stable artificial radioisotope is 11C, which has a half-life of 20.34 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. Lighter isotopes exhibit beta-plus decay into isotopes of boron and heavier ones beta-minus decay into isotopes of nitrogen, though at the limits particle emission occurs as well. The two lightest isotopes decay into helium via short-lived isotopes of lithium, beryllium and boron.
List of isotopes
Carbon-11
Carbon-11 or 11C is a radioactive isotope of carbon that decays to boron-11 with a half-life to 20.34 minutes. This decay mainly occurs due to positron emission, with around 0.19–0.23% of decays instead occurring by electron capture.
11C → 11B + e+ + νe + 0.96 MeV
11C + e− → 11B + νe + 1.98 MeV
It is produced by hitting nitrogen with protons of around 16.5 MeV in a cyclotron. The causes the endothermic reaction
14N + p → 11C + 4He − 2.92 MeV
It can also be produced by fragmentation of 12C by shooting high-energy 12C at a target.
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