Definition of Thermoluminescence
Thermoluminescence is the emission of light by a crystalline material when it is heated, after having previously absorbed energy from ionizing radiation. This light release occurs at temperatures below those required for incandescence and is a result of stored energy from the radiation exposure.
The Mechanism of Thermoluminescence
When a thermoluminescent material is exposed to radiation, electrons are excited to higher energy levels and become trapped in defects within the crystal lattice. These 'electron traps' are stable at ambient temperatures. Upon subsequent heating, thermal energy liberates the trapped electrons, allowing them to return to their ground states and emit photons of light.
Key Applications of Thermoluminescence
Thermoluminescence has two primary applications: radiation dosimetry and archaeological/geological dating. In dosimetry, it measures the cumulative radiation dose received by individuals or equipment. For dating, it helps determine the age of ancient artifacts like pottery or burnt flint by measuring the radiation accumulated since their last heating event.
Factors Influencing Thermoluminescence Emission
The intensity of the emitted light is directly proportional to the amount of radiation absorbed by the material, making it a quantitative measurement. Factors such as the specific material (e.g., quartz, feldspar, LiF), the heating rate, and the temperature reached during analysis critically affect the thermoluminescent signal. Each material has a characteristic 'glow curve' when heated.