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Joukowsky Institute for Archaeology & the Ancient World
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Providence, RI 02912
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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. 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. 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. 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 major source of error in establishing dates from thermoluminescence is a consequence of inaccurate measurements of the radiation acting on a specimen. The complex history of radioactive force on a sample can be difficult to estimate. However, thermoluminescence proven acceptable in providing approximate dates in the absence of more exact measures.
“Dating In Exposed and Surface Contexts”, ed.: Beck, Charlotte. University of New Mexico Press: Albuquerque, NM, 1994.
Michels, Joseph. “Dating Methods in Archaeology”. Seminar Press, New York: NY, 1973