The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
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Thermoluminescence is phosphorescence of a material due to heating.
Thermoluminescence occurs as a result of high-energy electrons trapped within the material being studied. The electrons are trapped at metastable sites within the mineral lattice of the material. When the material is heated the electrons are freed and this produces light very similar in quantity and quality to that of fluorescence. The amount of light produced is proportional to the energy that the material has absorbed as a result of exposure to ionizing radiation. While the mineral is at standard temperature and pressure the electrons are trapped inside the mineral and there is no thermoluminescence. The thermoluminescence does not manifest itself until a temperature of 932°F (500°C) is reached. The electrons are released at this temperature and they are able to return to their normal atomic orbits. As they do this photons of light are emitted in the visible spectrum.
A graph plotting light against temperature is called a glow curve and it is characteristic of a given mineral. The amount of light emitted is proportional to the sensitivity of the material and the amount of radiation absorbed. Comparison between the sample under test and a sample with a known amount of added radiation can be made to give an indication of when the sample was last exposed to ionizing radiation (a clock resetting event). A clock resetting event can be heating, so it can be calculated when a meteorite heated up in the atmosphere, or when a piece of pottery was fired, or when some material was burned.
Thermoluminescence is a technique which can be used to date material that has once been heated.