# Radiocarbon dating

## Description

A method used to estimate the age of carbon-containing materials. Radiocarbon dating was discovered by Willard Libby in 1947 (Nobel prize in chemistry 1960). It is based on the measurement of the proportion of the isotope carbon-14 in the total carbon content of the concerned material. Carbon 14 is a naturally occurring radioactive carbon isotope produced by the interaction of cosmic rays (neutrons) with the stable nitrogen 14 present in the earth atmosphere. It is assumed that the proportion of carbon 14 in living plants and animals is in equilibrium with that of the atmosphere due to continual carbon dioxide exchanges with the air. Once the plant or animal dies and no new carbon 14 is assimilated by the plant or animal, the existing carbon 14 concentration decreases at a rate proportional to its radioactive decay. The radioactive period of carbon 14 is 5730 y. Two measurement methods of carbon 14 content are currently used for dating purposes: - Liquid scintillation, for which each measured sample must have a mass of about 10 to 100 g - Ion acceleration coupled with a mass spectrometer (AMS), a much more sensitive method, for which each measured sample can have a mass of about 1 to 20 mg Precise radiocarbon dating is checked and correlated with the measurement of materials of exactly known age like tree rings. The method is imprecise for dating recent materials (less than 500 y before present)but is well adapted and precise for dating ancient and prehistoric materials up to 50000 years old. Radiocarbon dating is been used to determine the ages of of wood, charcoal, seeds, pollen, foraminifers, textiles, bones (carbonised or not), teeth, ivory, hair, leather, basketwork, peat, shells, coral, any archaeological organic remains…

## Synonyms and Related Terms

carbon-14 dating; radiometric dating; datation par le carbone 14 (Fr.); Kohlenstoff 14 Altersbestimmung (Deut.)

## Other Properties

Carbon-14 has a half life of 5730 years.

## Additional Information

° Protsch and Berger, *Science*, 179:4070 p.235-239, 1973. ° Roy Switzur "Dating Techniques" Building Conservation Directory 2001: Link