Thermoluminescence datingThermoluminescence dating is the determination of the date at which materials were formed by measuring the light energy released when heating it.
The natural flux of ionizing radiation - both from cosmic radiation as well as natural radioactivity - can put crystalline structures in excited states storing some of the energy of the radiation. A very small fraction can stay in these excited states for long time. When such material is heated the stored energy is released as weak light, the so called thermoluminescence. After cooling and re-heating it will not show the light anymore, as no excited states remain.
Thermoluminescence dating is used for material where radiocarbon dating is not available, like sediments.