ġ4C is unstable and decays back to 14N, at the rate of 50% every 5,730 years (so after 11,460 years 25% will be left, after 17,190 years 12.5% will be left, and so on). The technique is based on comparing the levels of 14C and 12C isotopes in the sample.ġ4C is produced in the atmosphere by cosmic ray neutrons replacing a proton in nitrogen ( 14N), producing 14C.
The first-order decay curve of carbon-14 based on the half-life of 5730 years.