Radiocarbon Dating

Schema

The isotope with mass 14, known as radiocarbon, is one of the unstable isotopes of carbon with widespread applications in the scientific world. The use of 14C as a „clock” for estimating the age of various historical and pre-historical samples is one of its most important applications.

Willard F. Libby was the father of the radiocarbon dating method who mentioned the possibility to date the carbon based samples for the first time in May 1947 within the “Science” journal and then applied this method for the first time in 1949. For his scientific contribution W.F. Libby was awarded with the Nobel Prize in Chemistry in 1960.

Small amounts of 14C are generated in the upper layers of the atmosphere under the influence of cosmic rays, especially high energy protons, being produced as a result of the interaction of radiation with the most abundant element of the atmosphere, 14N. The resulted radiocarbon chemically reacts with oxygen to form 14CO2 which enters the global cycle of carbon in nature.

During their lifetime, plants and animals intake 14C from the carbon dioxide present in the atmosphere, from water and nutrients, reaching an equilibrium level of 14C with the environment (~1.2*10-12 from 12C). Once the organism stops living, the carbon exchange with the environment stops as well, thus the concentration of radiocarbon from the organism decreases at a specific rate described by the radioactive decay law with a known half-life T1/2 = 5730 years.

From 1949 to 1977 all radiocarbon dating analysis were made by radiometric measurements. From 1977, the radiocarbon dating method that makes use of a particle accelerator, also known as Accelerator Mass Spectrometry method, gained a lot of notoriety. Among the advantages of this method we can name reduced analysis time, here including also chemical preparation of the samples, the amounts of necessary dating material (a few grams to milligrams) and high measurement accuracy.

The radiocarbon dating laboratory RoAMS from IFIN-HH applies the AMS dating technique using a 1MV Tandetron Accelerator (produced by High Voltage Engineering Europe). The radiocarbon dating method AMS implies counting atom by atom 12C, 13C and 14C species from the sample in order to determine the isotopic ratios. Measurement efficiency can reach 10 -15 (14C/12C) which makes AMS the most sensitive radiocarbon dating method.

Radiocarbon calibration: OxCal, Calib