Thermoluminescence dating methods
Heating the mineral (or exposure to light) releases electrons, and produces a flash of light, setting the clock to 0 (maybe only partial).Thereafter, luminescence accumulation is proportional to age.Used particularly for edu.au/environment/ee Pages/ee Dating/Quaternary Geochronology/ Trapped Charge Dating PRINCIPAL: energy trapped in crystal imperfections depends on dose rate and time. establish hydration rate for each type of obsidian by examining pieces of known age, or with high pressure and temperature in lab.When pottery gets covered in the ground, radiation from the earth starts to energize (excite) the electrons of these crystalline materials, putting them into “trap states.” This is a measure of the radiation dose.An input of energy, such as heat, is required to free these trapped electrons.
Because this accumulation of trapped electrons begins with the formation of the crystal structure, thermoluminescence can date crystalline materials to their date of formation; for ceramics, this is the moment they are fired.
By comparing this light output with that produced by known doses of radiation, the amount of radiation absorbed by the material may be found.
Most mineral materials, including the constituents of pottery, have the property of thermoluminescence (TL), where part of the energy from radioactive decay in and around the mineral is stored (in the form of trapped electrons) and later released as light upon strong heating (as the electrons are detrapped and combine with lattice ions).
Warning about fakes using ancient materials What about airport x-rays and radiography? Thus, when one measures dose in pottery, it is the dose accumulated since it was fired, unless there was a subsequent reheating.
When pottery is fired, it loses all its previously acquired TL, and on cooling the TL begins again to build up.
The longer the pottery is in the ground, the more radiation dose it will absorb, causing more electrons to be excited into trap states.