Thermo luminescence dating
The most common methods are: • The standard method (Aitken, 1985) performs regression analyses for both growth curves and the sum of their absolute values essentially provide the paleodose.• The normalization method (Valladas & Gillot, 1978; Valladas, 1992; Mercier, 1991), one of the two growth curves is shifted towards the other until they are matched, and the amount of the shift essentially gives paleodose.A non-negligible part of materials which ceramic is usually made of (like quartz and feldspars) is thermoluminescent: those materials have trap states that can capture electrons after interaction with alfa, beta and gamma rays existing in nature.When these materials are heated to several hundreds of Centigrade degrees, electrons are evicted from trap states and energy is emitted in form of light: thermoluminescence (TL).The accuracy of the linearity in heating sample is crucial to have a precise measure.The result of this measure is, as described above, a glow curve.
An input of energy, such as heat, is required to free these trapped electrons.
The wavelength of the emitted light is characteristic of the luminescent substance and not of the incident radiation.
Thermoluminescence (TL) is the process in which a mineral emits light while it is being heated: it is a stimulated emission process occurring when the thermally excited emission of light follows the previous absorption of energy from radiation.
Heating ceramic in a furnace resets TL accumulated by clay and other materials; from this time on, TL begins growing again as time passes; the more concentrated radioactivity where ceramic is, the quicker TL grows.
Thus by measuring TL we can date an object since the last time it was heated above 400°C.