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Radiocarbon dating 14C |
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Radiocarbon formed in the upper atmosphere is oxidized to 14CO2. The rate is between 1.7 and 2.5 atoms/cm2/s. After mixing with atmospheric CO2 (0.03 vol %), it becomes part of the carbon cycle in the biosphere. Assimilated by plants, it enters the food chain and thus becomes part of all living organic matter. Except for slight isotopic fractionation, which can be corrected, the specific activity of 14C in terrestrial organic matter is the same as in atmospheric carbon dioxide. Charcoal, wood, seeds, bone, ivory, horn, humus, peat, leaves, resin, lichen, tissue, hair, secondary carbonate, shells, egg, soil and sediment, as well as groundwater and ice can be dated, in the age range of 100 to 40,000 years. By following equation: A = A0 exp (- l t) one can calculate elapsed time from initial A0 activity to final A. Further correction and calibration is used, as well. Measurements are performed by proportional counters within a very low background chamber. |
