Thermoluminescence

Physics

High energy radiation creates electronic excited states in crystalline materials. In some materials, these states are trapped, or arrested, for extended periods of time by localized defects, or imperfections, in the lattice interrupting the normal intermolecular or inter-atomic interactions in the crystal lattice. Quantum-mechanically, these states are stationary states which have no formal time dependence; however, they are not stable energetically, as vacuum fluctuations are always "prodding" these states. Heating the material enables the trapped states to interact with phonons, i.e. lattice vibrations, to rapidly decay into lower-energy states, causing the emission of photons in the process.

Use in dating

Main article: Thermoluminescence dating, Thermoluminescent dosimeter

The amount of luminescence is proportional to the original dose of radiation received. In thermoluminescence dating, this can be used to date buried objects that have been heated in the past, since the ionizing dose received from radioactive elements in the soil or from cosmic rays is proportional to age. This phenomenon has been applied in the thermoluminescent dosimeter, a device to measure the radiation dose received by a chip of suitable material that is carried by a person or placed with an object.

Thermoluminescence is a common geochronology tool for dating pottery or other fired archeological materials, as heat empties or resets the thermoluminescent signature of the material (Figure 1). Subsequent recharging of this material from ambient radiation can then be empirically dated by the equation:

Age = (subsequently accumulated dose of ambient radiation) / (dose accumulated per year)

This technique was modified for use as a passive sand migration analysis tool (Figure 2). |url-access=subscription

References

References

1. [http://www.signonsandiego.com/news/science/20061225-0031-waikikisand.html Waikiki sand]