Thermoluminescence dating ceramics

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.The paleodose is the absorbed dose of natural radiation accumulate by a sample.This paleodose is determined from the TL signal measured by heating sample at a constant rate.These give rise to an external dose rate in addition to the one from secondary cosmic rays.Obsidian is the volcanic glass that was sometimes used as raw material for the manufacture of stone tools.Since measured TL depends on time of exposition to natural radiations but also on the intensity of these radiations, to achieve a precise dating we need information about radioactivity of the area where the object was found.During TL analysis, the sample is reheated by a controlled heating process, so the energy is released in the form of light (thermoluminescence) as the electrons escape.

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).Energy absorbed from ionising radiation (alpha, beta, gamma, cosmic rays) frees electrons to move through the crystal lattice and some are trapped at imperfections in the lattice.Subsequent heating of the crystal can release some of these trapped electrons with an associated emission of light.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.

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