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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.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.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.Internal dose rate consists of three parameters related to the α, β and γ radiation, where the latter is usually small in most cases.
When a specimen is reheated, the trapped energy is released in the form of light (thermoluminescence) as the electrons escape.
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.
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.
The amount of light produced is a specific and measurable phenomenon.