AMS Radiocarbon Dating
Definition
Accelerator Mass Spectrometry measurement of the ratio of carbon-14 to carbon-12 in a sample. It requires milligram-scale samples and produces a raw radiocarbon age that must be calibrated against a reference curve (IntCal20) to yield a calendar-year range.
- Instrument
- Accelerator Mass Spectrometer
- Measures
- 14C to 12C ratio
- Sample size
- Milligram scale
- Calibration curve
- IntCal20
Common questions
Why does a raw AMS result need calibration before it means anything forensically?+
Atmospheric 14C production has varied over time, so a raw radiocarbon age is not a calendar date. It must be run through a calibration curve built from tree rings and other dated records to convert it into a calendar-year range with an associated probability.
How does AMS differ from older decay-counting radiocarbon methods?+
AMS counts 14C atoms directly with a mass spectrometer rather than waiting for radioactive decay events, which is far faster and works on samples orders of magnitude smaller than the gas-counting or liquid scintillation methods it replaced.
Related terms
- Bomb-Pulse Dating
- Use of the post-1952 atmospheric 14C spike, produced by nuclear weapons testing, to date biological tissues formed since 1950. Because the spike...
- Calibration Curve
- In RIA, a set of standards containing known concentrations of unlabelled analyte that are run alongside test samples. Bound radioactivity is measured...
- Dendrochronology
- The science of dating by tree-ring sequences. Each annual ring encodes the growing conditions of that year; matching ring patterns to a...
- OSL (Optically Stimulated Luminescence)
- A dating method that measures the accumulated radiation dose stored in mineral grains (usually quartz or feldspar) since they were last exposed...
- Terminus Post Quem (TPQ)
- Latin for 'limit after which.' The date of the youngest datable item in a context sets the earliest possible date for the...