Carbon isotope

Main isotopes of carbon

iso NA half-life DM DE (MeV) DP 11C syn 20 min β+ 0.96 11B 12C 98.9% is stable with 6 neutrons 13C 1.1% is stable with 7 neutrons 14C trace 5730 y β− 0.156 14N
Standard atomic weight (Ar)	[12.0096, 12.0116] Conventional: 12.011

Carbon (₆C) has 15 known isotopes, from ⁸C to ²²C, of which ¹²C and ¹³C are stable. The longest-lived radioisotope is ¹⁴C, with a half-life of 5,700 years. This is also the only carbon radioisotope found in nature—trace quantities are formed cosmogenically by the reaction ¹⁴N + ¹n → ¹⁴C + ¹H. The most stable artificial radioisotope is ¹¹C, which has a half-life of 20.334 minutes. All other radioisotopes have half-lives under 20 seconds, most less than 200 milliseconds. The least stable isotope is ⁸C, with a half-life of 2.0 x 10⁻²¹ s.

Carbon-11 or ¹¹C is a radioactive isotope of carbon that decays to boron-11. This decay mainly occurs due to positron emission; however, around 0.19–0.23% of the time, it is a result of electron capture. It has a half-life of 20.334 minutes.

It is produced from nitrogen in a cyclotron by the reaction

Carbon-11 is commonly used as a radioisotope for the radioactive labeling of molecules in positron emission tomography. Among the many molecules used in this context is the radioligand [11
C
]DASB.

There are three naturally occurring isotopes of carbon: 12, 13, and 14. ¹²C and ¹³C are stable, occurring in a natural proportion of approximately 99:1. ¹⁴C 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. Isotopically, ¹⁴C constitutes a negligible part; but, since it is radioactive with a half-life of 5,700 years, it is radiometrically detectable. Since dead tissue doesn't absorb ¹⁴C, the amount of ¹⁴C is one of the methods used within the field of archeology for radiometric dating of biological material.

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