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=== Radiocarbon dating === A brief synopsis of the radiocarbon dating process provides a useful context for clearer understanding of how the CEGS fits in. So, what must be done to a sample in order to date it? It undergoes a series of functional phases: ==== Pretreatment ==== First, a representative fraction of the submitted material is isolated for further processing. Any carbon-bearing matter that might be older or younger than the target fraction must be removed. Often, specific carbon compounds are selected by employing chemical reagents to separate them from the other substances present. Additionally, steps may be taken to remove or avoid the formation of non-carbonaceous chemicals that might interfere with subsequent steps. This phase is sometimes called "wet chemistry". ==== Extraction ==== After pretreament, the sample's carbon must be separated from the rest of the sample material. To obtain an accurate analysis, all non-sample carbon, such as CO<sub>2</sub> from the air, must be excluded. A vacuum system is usually employed to remove air, and carbon-free gases such as research-grade oxygen, helium, argon, or nitrogen are introduced to participate in the extraction. The collected carbon must come exclusively from the sample material. Moreover, all of the the sample's carbon must be collected. Due to fractionation effects, an incomplete or partial carbon extraction can compromise the result as well. The technique for liberating the carbon from pretreated material varies based on the type of sample, but most commonly it is either combusted (burned) or digested in acid. In either case, oxygen combines with the carbon to form carbon dioxide (CO<sub>2</sub>). Other chemical reactions usually take place simultaneously, so steps are taken to remove unwanted reaction products, such as water, sulfur and halogen compounds, nitrogen oxides, and so on. To summarize in simple terms, extraction consists of carbon {{HoverText|Getting the carbon out of the sample.|liberation}}, CO<sub>2</sub> {{HoverText|Capturing the liberated carbon dioxide.|collection}}, and {{HoverText|Removing everything else, except oxygen.|purification}}. ==== Graphitization ==== This phase uses hydrogen to remove the oxygen from the purified CO<sub>2</sub>, leaving behind solid carbon. The carbon is deposited onto powdered iron, which serves as a catalyst for the reduction and a substrate for the deposition. The solid carbon is commonly called "graphite", although this term is not strictly correct, because it doesn't have a layered graphene structure. ==== Isotope Analysis ==== Finally, the "graphite" is compressed into a tiny, cylindrical aluminum "cathode" or "target" and inserted into the ion source of an accelerator mass spectrometer. Ionized cesium is sputtered onto the graphite's surface, which ionizes the carbon atoms. Electric fields focus and accelerate the charged atoms through a strong magnet which deflects them toward a set of particle detectors. The lightest atoms (<sup>12</sup>C) are deflected more than the heaviest ones (<sup>14</sup>C), so they go into different detectors. The ratio of <sup>14</sup>C atoms to <sup>12</sup>C in the sample is then used to determine its age.
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