Carbon-14 also reveals whether a sample of ivory was removed from an animal before or after the 1989 ban on ivory sales.
Accelorator mass spectrometry for dating
The ratio of unstable carbon-14 to stable carbon-12 atoms reveals the age of the sample—be it an ancient manuscript or a Neanderthal skull.
Likewise, other isotopes like beryllium-10 and aluminum-26 divulge how long a sample has been subjected to the constant barrage of cosmic rays that comes with sitting on the surface of Earth—telling geologists, for example, how quickly a region of rock is eroding or how long ago an earthquake brought sediment to the surface.
DR CHRISTINE PRIOR In conventional radiocarbon dating, you’re measuring the presence of the C-14 when you measure the radioactive decay.
The C-14 decays with the beta particle, and you have some detection equipment and you count the C-14s one by one.
An accelerator then increases the kinetic energy of the carbon ions to 10-30 million electron volts and moves them through a tube where a powerful electromagnet makes them change direction. Because carbon-14 decays over time, the amount of it in a sample indicates the age of the sample.
How much their path bends depends on their mass: Lighter ions bend more. Penn State will soon be home to an accelerator mass spectrometer (AMS) that will allow researchers all over the country to do high-precision carbon dating to address questions about Earth's past and present.
A mass spectrometer is an instrument that uses a series of magnets to bend a beam of ions and then physically count how many there are, so with AMS radiocarbon dating, we can measure a carbon-12, 13 and 14 beam, and we measure the ratio of 14 to 13, and from that, we can tell how much C-14 is in the sample.
So the most important things about AMS radiocarbon dating as opposed to conventional is that the sample size is much, much smaller.
CAMS is one of several dozen labs worldwide that conduct accelerator mass spectrometry, or AMS.
The technique is less time-consuming and requires a much smaller sample size than traditional carbon dating.
Dr Christine Prior is Team Leader of the Rafter Radiocarbon Laboratory at GNS Science.