ANP 203 Lecture Notes - Lecture 12: Accelerator Mass Spectrometry, Cosmic Ray, Speleothem
Document Summary
After death: no addition of atmospheric 14 c, radioactive decay of existing 14 c. 14 c has a half life of 5730 years. 14 c - organic remains(wood, charcoal, shells, bone, fiber, hair, hide, etc) Decay counting is relatively insensitive and subject to large statistical uncertainties for small samples. When there is little 14 c to begin with, the long radiocarbon half-life means that very few of the 14 c atoms will decay during the time allotted for their detection, resulting in few disintegrations per minute. Accelerator mass spectrometry (ams) - 14 c atoms can be detected and counted directly vs. only detecting those atoms that decay during the time interval allotted for an analysis. Ams allows dating samples containing only a few milligrams of carbon. Radiocarbon dating laboratories generally report an uncertainty for each date. For example, 3000 30 bp indicates a standard deviation of 30 radiocarbon years.
