short-lived resonance with a half-life of ; it primarily decays back into its three constituent alpha particles, though 0.0413% of decays (or 1 in 2421.3) occur by internal conversion into the ground state of 12C. In 2011, an ab initio calculation of the low-lying states of carbon-12 found (in addition to the ground and excited spin-2 state) a resonance with all of the properties of the Hoyle state. Isotopic purification The isotopes of carbon can be separated in the form of carbon dioxide gas by cascaded chemical exchange reactions with amine carbamate. See also Avogadro constant Carbon-11 Carbon-13 Carbon-14 Isotopes of carbon Isotopically pure diamond Mole (unit) References External links Isotopes of carbon