is a technique used by scientists to learn the ages of biological specimens – for example, wooden archaeological artifacts or ancient human remains – from the distant past.
It can be used on objects as old as about 62,000 years.
The internationally accepted radiocarbon dating reference is 95% of the activity, in 1950 AD, of the NBS oxalic acid normalized to C activity: » 50 pmc Chemical and isotopc evolution in recharge zone: (Fig) (Fig) Open and closed system conditions ‘real world’ systems are somewhere in between open and closed and the correction models mentioned above and described in Clark and Fritz (chapter 8) have to be applied.
C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.
In this method, the activity of radioactive carbon ( carbon-14) present in bones, wood, or ash found in archaeological sites is measured.
When they die, they stop exchanging carbon with the biosphere and their carbon 14 content then starts to decrease at a rate determined by the law of radioactive decay.
Different isotopes tend to concentrate in particular organs: for example, iodine-131 settles in the thyroid gland and can reveal a variety of defects in thyroid functioning.
Another isotope, carbon-14, is useful in studying abnormalities of metabolism that underlie diabetes, gout, anemia, and acromegaly.
It was discovered in 1934 by Grosse as an unknown activity in the mineral endialyte. This half life has later been re-determined by Godwin. Libby recognized that due to its occurrence in natural materials, either by simple mixing processes or by carbon exchange.
In the same year, Kurie (Yale) exposed nitrogen to fast neutrons and observed long tracks in a bubble chamber. The mean life time of roughly 8000 years is ideal for dating of reservoirs that are a few decades to a few ten thousand yeas old.
Radiocarbon dating uses isotopes of the element carbon. Cosmic rays – high energy particles from beyond the solar system – bombard Earth’s upper atmosphere continually, in the process creating the unstable carbon-14. Because it’s unstable, carbon-14 will eventually decay back to carbon-12 isotopes.