Advantages and disadvantages of radiocarbon dating
At the terminal they pass through either a very thin carbon film or a tube filled with gas at low pressure (the stripper), depending on the particular accelerator.
Collisions with carbon or gas atoms in the stripper remove several electrons from the carbon ions, changing their polarity from negative to positive. The positive ions are then accelerated through the second stage of the accelerator, reaching kinetic energies of the order of 10 to 30 million electron volts. This problem is solved in the tandem accelerator at the stripper –if three or more electrons are removed from the molecular ions the molecules dissociate into their component atoms. The kinetic energy that had accumulated up to now is distributed among the separate atoms, none of which has the same energy as a single C from the more intense "background" caused by the dissociated molecules on the basis of their kinetic energy.
Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
However, the more dating methods we can use, the more likely it is that our timeframe will be reliable.
Any dating method is only possible when the right sort of material is present (for example, there is no possibility of using radiocarbon or dendrochronology when there is no organic matter or preserved wood available).
Accelerating the ions to high energy has one more advantage.
At the kinetic energies typically used in an AMS system it is possible to use well-established nuclear physics techniques to detect the individual C ions as they arrive at a suitable particle detector.
Obviously, this works only for things which were once living.
Chronometric Dating for the Archaeologist isn't bedtime reading, nor is it for the faint-of-heart, but at the same time one does not have to have a background in materials science or organic or inorganic chemistry to understand the basic premise of the work.
The editors' goal is to present a factual, current, and well-documented evaluation of a dozen of the major techniques that are used by scientists to determine chronology from archaeological artifacts or contexts.
This may be a solid-state detector or a device based on the gridded ionisation chamber.
The latter type of detector can measure both the total energy of the incoming ion, and also the rate at which it slows down as it passes through the gas-filled detector.