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The dose rate includes an internal component (short- ranged alpha and beta irradiation) from the sample itself and an external component (long-ranged gammas and cosmic radiation) from the environment.
The age equation is expressed as a simple ratio: Age (ka) = De (Gy) / DR (Gy/ka) where De is the equivalent dose in grays (unit of absorbed dose), and DR is the average dose rate over time. Equivalent dose is the amount of radiation dose that is necessary to account for the measured luminescence signal, in other words, how much radiation is needed to get from zero luminescence to the current, natural luminescence. De is measured by calibrating the natural signal against laboratory-administered radiation.
This in turn is proportional to the amount of absorbed radiation, which can be related to time if the average dose rate per unit time can be estimated.
The latter includes stimulus not only from the visible spectrum but from ultraviolet and infrared radiation as well.
Because traps have different energy depths, some traps are not very stable at ambient temperatures and lose their electrons over the time period relevant to archaeology.
Other traps are sufficiently deep that they are not easily emptied during the exposure to heat or light.
Recent advances in methodology and instrumentation have improved both its accuracy and precision, such that it is now becoming an important player in Quaternary science.
The advantage luminescence has over other techniques is the ability to date directly events of archaeological and geological interest: the last heating of ceramics and lithics and the last exposure of light for sediments.