Radiation used carbon dating
When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons.
The resulting neutrons ( but attempts to measure the production rate directly in situ were not very successful.
Small amounts of carbon-14 are not easily detected by typical Geiger–Müller (G-M) detectors; it is estimated that G-M detectors will not normally detect contamination of less than about 100,000 disintegrations per minute (0.05 µCi).
Liquid scintillation counting is the preferred method.
Carbon dioxide is distributed on a worldwide basis into various atmospheric, biospheric, and hydrospheric reservoirs on a time scale much shorter than its half-life.
Measurements have shown that in recent history, radiocarbon levels have remained relatively constant in most of the biosphere due to the metabolic processes in living organisms and the relatively rapid turnover of carbonates in surface ocean waters.
Radiocarbon dating estimates can be obtained on wood, charcoal, marine and freshwater shells, bone and antler, and peat and organic-bearing sediments.
They can also be obtained from carbonate deposits such as tufa, calcite, marl, dissolved carbon dioxide, and carbonates in ocean, lake and groundwater sources.
The amount of C-14 is compared to the amount of C-12, the stable form of carbon, to determine how much radiocarbon has decayed, thereby dating the artifact.Each sample type has specific problems associated with its use for dating purposes, including contamination and special environmental effects.More information on the sources of error in carbon dating are presented at the bottom of this page.These are relatively low energies; the maximum distance traveled is estimated to be 22 cm in air and 0.27 mm in body tissue.The fraction of the radiation transmitted through the dead skin layer is estimated to be 0.11.