Thermoluminescence tl dating

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.

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).

These crystalline solids are constantly subjected to ionizing radiation from their environment, which causes some energized electrons to become trapped in defects in the molecular crystal structure.

An input of energy, such as heat, is required to free these trapped electrons.

The accumulation of trapped electrons, and the gaps left behind in the spaces they vacated, occurs at a measurable rate proportional to the radiation received from a specimen’s immediate environment.

When a specimen is reheated, the trapped energy is released in the form of light (thermoluminescence) as the electrons escape.

The amount of light produced is a specific and measurable phenomenon.

Material and objects of archaeological or historical interest that can be dated by thermoluminescence analysis are ceramics, brick, hearths, fire pits, kiln and smelter walls, heat treated flint or other heat-processed materials, the residues of industrial activity such as slag, incidentally fire-cracked rocks, and even originally unfired materials such adobe and daub if they had been heated in an accidental fire.

The accuracy of the linearity in heating sample is crucial to have a precise measure.

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