Optical luminescence dating laboratory
Heating these crystals (such as when a pottery vessel is fired or when rocks are heated) empties the stored energy, after which time the mineral begins absorbing energy again.
TL dating is a matter of comparing the energy stored in a crystal to what "ought" to be there, thereby coming up with a date-of-last-heated.
But when the rock is exposed to high enough levels of heat or light, that exposure causes vibrations in the mineral lattices and the trapped electrons are freed.
The exposure to radioactive elements continues, and the minerals begin again storing free electrons in their structures.
If you can measure the rate of acquisition of the stored energy, you can figure out how long it has been since the exposure happened.
Materials of geological origin will have absorbed considerable quantities of radiation since their formation, so any human-caused exposure to heat or light will reset the luminescence clock considerably more recently than that since only the energy stored since the event will be recorded.
The term luminescence refers to the energy emitted as light from minerals such as quartz and feldspar after they've been exposed to an ionizing radiation of some sort.
Two forms of luminescence dating are used by archaeologists to date events in the past: thermoluminescence (TL) or thermally stimulated luminescence (TSL), which measures energy emitted after an object has been exposed to temperatures between 400 and 500°C; and optically stimulated luminescence (OSL), which measures energy emitted after an object has been exposed to daylight.The way you measure energy stored in an object that you expect has been exposed to heat or light in the past is to stimulate that object again and measure the amount of energy released.The energy released by stimulating the crystals is expressed in light (luminescence).Located in the basement of Bessey Hall on UNL's City Campus, the Luminescence Geochronology Laboratory specializes in optically-stimulated luminescence (OSL) dating of Quaternary fluvial, eolian, and coastal deposits.This "dark (amber-light only) lab" contains rooms for sample storage, sample preparation, and OSL readers. This lab primarily serves UNL faculty and graduate students, but collaborative research is ongoing with colleagues from other institutions.
The OSL laboratory is now a key research facility of the Department of Geography and Planning in the School of Environmental Sciences.