Accelerator techniques for carbon dating

08 Dec

Bone is an ideal material for the new technique, since amino acids can normally be isolated and purified from gram-size samples.

Studies of the origins of domestication are aided by the dating of individual grains and seeds.

The technique of comparing the abundance ratio of a radioactive isotope to a reference isotope to determine the age of a material is called radioactive dating.

Many isotopes have been studied, probing a wide range of time scales.

The boat of a pharaoh was discovered in a sealed crypt and reassembled in a museum near the pyramids (see Fig. The age of our galaxy and earth also can be estimated using radioactive dating.

This article is reproduced from Nuclear News, June 19998, and is based on a paper presented at the ANS Winter Meeting, held November 16-20, 1997, in Albuquerquete N. AMS has become an accurate and precise method for dating many types of materials - including such interesting items as the Shroud of Turin and the Dead Sea Scrolls, which will be discussed later—where only a small sample can be spared.An accelerator mass spectrometer measures the amounts of different isotopes within a sample.For carbon dating, the process starts in an ionizing chamber, where the atoms within a sample of pure carbon are given a negative charge.For scientists whose test material is rare, valuable, or extremely hard to collect, that's important.Douglas Kennett, professor of anthropology at Penn State, recently confirmed a correlation between the Maya Long Count calendar and the European calendar by AMS dating small slivers of wood from a carved Maya lintel.The machines can now operate to about ± 80 years or better.Dates older than 40,000 years have not yet been achieved, but the ability to use small samples has already had considerable impact on dating the period 10,000–30,000 years ago.Katherine Freeman, distinguished professor of geosciences at Penn State, uses it to follow crude oil compounds released from the 2010 Deepwater Horizon oil spill that were taken up by microbes living in sediments of the Gulf of Mexico.More traditional uses of carbon dating also benefit from an AMS, because it provides more precise measurements of carbon-14 than other methods, and it can do so with incredibly tiny samples -- as small as 1 milligram.C atoms, rather than the conventional counting of radioactive disintegrations.The result is that samples up to 1000 times smaller can be handled.