Thermoluminescence dating method (Answer in 150 words)

- Thermoluminescence dating method (Answer in 150 words)
Introduction
Thermoluminescence dates the last occasion on which a material was strongly heated. It is the principal absolute method for fired archaeological materials lying outside the reach of radiocarbon.
Body
1. The principle: radiation from uranium, thorium and potassium in the sample and its burial matrix displaces electrons, trapped at lattice defects in quartz and feldspar. Heating above about 500 degrees Celsius empties the traps, releasing the energy as light and resetting the clock; charge then rebuilds with time.
2. The procedure: the sample is lifted without exposure to light or heat, and the palaeodose measured by additive or regenerative dosing against a calibrated source. The annual dose rate is measured on site by gamma spectrometry, with moisture correction. Age equals palaeodose divided by annual dose.
3. Materials, range and limits: pottery, burnt flint, hearth stones, bricks and slag, over roughly 300 to 500,000 years, with errors near ten per cent. It assumes complete zeroing.
Conclusion
Thermoluminescence is less precise than radiocarbon but reaches much further back and dates the artefact itself. Its reliability turns on the burial dose rate being measured correctly.