Carbon-13, a stable, nonradioactive isotope with six protons and seven neutrons, makes up another one percent.
The tiny amount left, only one carbon atom in a trillion, is carbon-14.
"Even though there are carbon-14 facilities around the world, science is still under-served," says Freeman.
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.
Soon, Penn State will complete the preparation process by converting the carbon dioxide to graphite targets that will be analyzed by the new AMS.
By the time the Penn State AMS facility is running at full tilt, it will be able to process and analyze up to 10,000 samples a year, from forensic cases, archaeological digs, and studies involving soil, sediment, water, and air.
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.