Accelerator mass spectrometry radiocarbon dating

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These reservoir effects are in part mitigated by the use of various calibration algorithms, such as the CALIB (When a radiocarbon lab returns a date from a sample such as 5568 BP, it does not mean that it dates to 3619 BC, because the true half-life of radiocarbon is 5730 years, and, more importantly, the proportion of radiocarbon in the atmosphere has varied through time, as discussed above.

So the calibration utilities are written to allow for differential in the absorption of C by different materials (i.e., marine shell versus wood charcoal), and to allow for different atmospheric effects.

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The basic instrumentation cost remains beyond the resources of individual laboratories or most pharmaceutical research companies.Using the CALIB 4.2 calibration, a radiocarbon assay of 5568 BP with a 1 standard deviation of 55 years on wood charcoal yields a date of: Note that there are two dates with ranges of a number of years.The range includes the one standard deviation, and the two dates are due to multiple intercepts on the calibration curve.Unlike the conventional organic mass spectrometry analyses described previously, AMS measures not molecules or their structural fragments, but the negatively charged , followed by its reduction to carbon (graphite).Negative ions sputtered from the graphitized sample are highly accelerated (millions of volts) toward a collision cell, where they are converted to positive ions through a charge-stripping process, and pass through a high-energy analyzing magnet to a Faraday cup detector, where their current can be accurately and precisely determined.

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