(14)C-modified compound
(14)c-modified compound
An isotopically modified compound in which the abundance of a <small><sup>14</small></sup>C isotope at one or more positions has been increased above that of the naturally occurring level (1 - 1.5 atoms for every 10<small><sup>12</small></sup> atoms of the carbon in the atmosphere). With a half-life of 5,700 years, <small><sup>14</small></sup>C is the longest-lived radioisotope of carbon.