Radioisotopes as tracers in carbon dating
The center employs a novel technique called Atom Trap Trace Analysis (ATTA) that captures and counts isotopes of the rare element krypton (Kr) to determine the age of ice and groundwater.One of only a few such devices in the world, it provides valuable information about the dynamics, flow rates and direction of water in aquifers, particularly those vital to arid regions. after four half lives only 1/16 or 5.5% of the isotope is left giving an age of 21,600 years.After seven half lives (37,200 years) there is less than 1% left (.6875% ).One radioactive substance that is very commonly used in hospitals is called technetium-99m.This emits gamma rays and has a half-life of 6 hours, both of which help to minimise the exposure of patients to radiation.These types of calculations can be done for any percentage of carbon 14 left in the wood.The accuracy of these calculation decreases as the percentage of the isotope left decreases.
For example, our bodies contain radioisotopes, such as potassium-40, which continuously emit radiation, but because the amount is very low, no damage is done.
The calculation of the age is dependent on assuming that the sample starts with 100% of the isotope.