Dating romance in tl
In the process of recombining with a lattice ion, they lose energy and emit photons (light quanta), detectable in the laboratory.
The amount of light produced is proportional to the number of trapped electrons that have been freed which is in turn proportional to the radiation dose accumulated.
Where there is a dip (a so-called "electron trap"), a free electron may be attracted and trapped.
The flux of ionizing radiation—both from cosmic radiation and from natural radioactivity—excites electrons from atoms in the crystal lattice into the conduction band where they can move freely.
Thermoluminescence emits a weak light signal that is proportional to the radiation dose absorbed by the material. The technique has wide application, and is relatively cheap at some US0–700 per object; ideally a number of samples are tested. The destruction of a relatively significant amount of sample material is necessary, which can be a limitation in the case of artworks.
The heating must have taken the object above 500° C, which covers most ceramics, although very high-fired porcelain creates other difficulties.
Optically stimulated luminescence dating is a related measurement method which replaces heating with exposure to intense light.Thermoluminescence testing involves heating a sample until it releases a type of light, which is then measured to determine the last time the item was heated.In thermoluminescence dating, these long-term traps are used to determine the age of materials: When irradiated crystalline material is again heated or exposed to strong light, the trapped electrons are given sufficient energy to escape.Most excited electrons will soon recombine with lattice ions, but some will be trapped, storing part of the energy of the radiation in the form of trapped electric charge (Figure 1).Depending on the depth of the traps (the energy required to free an electron from them) the storage time of trapped electrons will vary as some traps are sufficiently deep to store charge for hundreds of thousands of years.
Ideally this is assessed by measurements made at the precise findspot over a long period.