Optically stimulated luminescence

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In physics Optically stimulated luminescence or (OSL) is a method for measuring doses from ionizing radiation (commonly known as radioactive radiation).

The method makes use of electrons trapped between the valence and electron band in the crystaline structure of matter. Aluminum oxide is one such type of matter. The electrons become trapped with stimulation from high-frequency electromagnetic radiation (photons). The electrons are stimulated with light, giving them enough energy to free themselves from the trap. While escaping the trap, and returning to a stable position or another trap, excess energy is emitted with a photon (light). The photons are detected using a photomultiplier tube. The signal from the tube is then used to calculate the dose given to the material.

OSL is used in at least two entirely different applications: the dating of ancient materials (identical in purpose to the better known technique of radiocarbon dating), and as a method of radiation dosimetry which is the measurement of accumulated radiation dose in the tissues of health care, nuclear, research and other workers.

In dating two materials are mostly used: Quartz and feldspar.

The most popular OSL method is called Single-aliquot regeneration (or SAR). With this method the signal representing the unknown dose is read out. Then the sample is subjected to irradiation with a known dose, and the signal read again. The procedure is then repeated three times with different dosage. The signals from the known doses are then plotted as a function of dose, and the unknown dose can be read out of the curve.