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IGERT program in Archeological Science

Principles of AMS

Radiocarbon dating

Theory

Pretreatment

Measurement

Correction

Age Calculation

Calibration

Cosmogenic Radioisotopes

Publication

 
 
 

There are two correction factor that we apply on every sample:

Background Correction

     During the process of converting samples from their initial form to graphite, they acquire a samll amount of contamination, generally called background. To determine the magnitude of the contamination correction, blank targets are made from material containing no 14C and measurements are made of quantity

where the subscript B and std signify blank and standard quantities.

     The fraction modern of the sample, F, in terms of fraction modern, measured, Fm, can be expressed as

where

 

Background Correction

     By convention, the 13C isotopic fractionation in all samples is taken into account by normalizing to -25 per mil wrt PDB, the postulated mean value of terrestrial wood. The normalized specific activity of the sample, ASN relates to the measured sample activity AS as follows:

C variation in nature. (Stuiver and Polach, 1977)

 

    Another type of correction that we apply is when the reservoirs differ in specific 14C content from the atmosphere.

Reservoir Correction

     A reference to the geographic distribution of coastal region ΔR value (in 14C year) is shown in the graph :

(Stuiver and Braziuna, 1993)