Thermoluminescence dating of ceramics
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The thermoluminescence phenomenon arises from the irradiation of mineral inclusions by the radioactive impurities present in every ceramic paste, from the ejection of electrons due to this external energy supply, from the confinement of these electrons freed from the attraction of the nucleus into traps or deformations of the crystalline lattice, and finally from the return of the trapped electrons into the atoms owing to the external energy contribution resulting from the increase of temperature.
Limits The thermoluminescence is not very reliable in regards to the African and Chinese terracottas.
TL dating is a matter of comparing the energy stored in a crystal to what "ought" to be there, thereby coming up with a date-of-last-heated.
In the same way, more or less, OSL (optically stimulated luminescence) dating measures the last time an object was exposed to sunlight.
In the case of OSL sediment dating, suitable material (sand or silt-sized grains of quartz and feldspar) is usually available ubiquitously throughout the site.
Electrons from these substances get trapped in the mineral's crystalline structure, and continuing exposure of the rocks to these elements over time leads to predictable increases in the number of electrons caught in the matrices.
But when the rock is exposed to high enough levels of heat or light, that exposure causes vibrations in the mineral lattices and the trapped electrons are freed.
Better still, unlike radiocarbon dating, the effect luminescence dating measures increases with time.
As a result, there is no upper date limit set by the sensitivity of the method itself, although other factors may limit the method's feasibility.