Fractionation dating method
Ages are calculated using 5568 years as the half-life of radiocarbon and are reported without reservoir corrections or calibration to calendar years.For freeware programs, we suggest that you look at the following web site for a list of programs that will calibrate radiocarbon results to calendar years (including making reservoir corrections).[ Radiocarbon-Related Information Sources] The error in the age is given by 8033 times the relative error in the Fm .Therefore a 1% error in fraction-modern leads to an 80 year error in the age.Ages are rounded according to the convention of Stuiver & Polach, shown below.
One of the basic assumptions in carbon-14 dating is that the sample being analyzed has undergone only radioactive decay and has remained unaltered by any other process over the years since it ceased interaction with the biosphere. The archaeological artifacts and geological specimens sent to labs for radiocarbon dating are usually found embedded or buried with other materials that may have affected their radiocarbon content.
Any carbon-containing material that affects the carbon 14 content of any given sample is therefore a contaminant.
Important Note on Pretreatment – It is important to understand the pretreatments which are going to be applied to samples since they directly affect the final result.
In AMS, the filiamentous carbon or "graphite" derived from a sample is compressed into a small cavity in an aluminum "target" which acts as a cathode in the ion source.
The surface of the graphite is sputtered with heated, ionized cesium and the ions produced are extracted and accelerated in the AMS system.