Definition of luminescence dating dating curriculum
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 amount of light produced is measuered by a photomultiplier.The result is a glow curve showing the photon emission in function of the heating temperature: If the specimen’s sensitivity to ionizing radiation is known, as is the annual influx of radiation experienced by the specimen, the released thermoluminescence can be translated into a specific amount of time since the formation of the crystal structure.The interesting problem of luminescence will be discussed elsewhere.
Thus by measuring TL we can date an object since the last time it was heated above 400°C.Only if this proceeds rapidly enough does luminescence occur.Luminescence is more widespread in this phylum and more characteristic of the group as a whole than any other.If the heating rate is linear and if we suppose the probability of a second trapping to be negligible with respect to the probability of a recombination, the TL intensity is related to the activation energy of the trap level by a known expression. Thermoluminescence can be used to date materials containing crystalline minerals to a specific heating event.This is useful for ceramics, as it determines the date of firing, as well as for lava, or even sediments that were exposed to substantial sunlight.
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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.