Cyclotron sometimes used carbon dating
In mass analysis, a magnetic field is applied to these moving charged particles, which causes the particles to deflect from the path they are traveling.If the charged particles have the same velocity but different masses, as in the case of the carbon isotopes, the heavier particles are deflected least.At this stage, molecules that may be present are eliminated because they cannot exist in this triple charged state.The carbon atoms with triple positive charge further accelerate away from the positive terminal and pass through another set of focusing devices where mass analysis occurs.Reference materials are also pressed on metal discs.These metal discs are then mounted on a target wheel so they can be analyzed in sequence.Ions from a cesium gun are then fired at the target wheel, producing negatively ionized carbon atoms.
The negatively charged carbon atoms, however, move on to the stripper (a gas or a metal foil) where they lose the electrons and emerge as the triple, positively charged carbon atoms.
Thanks to nuclear physics, mass spectrometers have been fine-tuned to separate a rare isotope from an abundant neighboring mass, and accelerator mass spectrometry was born.
A method has finally been developed to detect carbon 14 in a given sample and ignore the more abundant isotopes that swamp the carbon 14 signal.
From these data, concentration ratio of the isotopes can be known to allow evaluation of the level of fractionation.
The greatest advantage that AMS radiocarbon dating has over radiometric methods is small sample size.