Of thermoluminescence dating
Energy absorbed from ionising radiation (alpha, beta, gamma, cosmic rays) frees electrons to move through the crystal lattice and some are trapped at imperfections in the lattice.
Subsequent heating of the crystal can release some of these trapped electrons with an associated emission of light.
The denominator Dose rate of the age formula consists of two independent parameters, the internal dose rate and the external dose rate.
Obviously, the denominator is crucial for the accurate determination of an age.
• The normalization method (Valladas & Gillot, 1978; Valladas, 1992; Mercier, 1991), one of the two growth curves is shifted towards the other until they are matched, and the amount of the shift essentially gives paleodose.
The paleodose is the absorbed dose of natural radiation accumulate by a sample.
This paleodose is determined from the TL signal measured by heating sample at a constant rate.
Three different types of glow curve can be distinguished: • The natural thermoluminescence of the sample as it is • The additive glow curve where a radiation does with a calibrate radioactive source is given in addition to the natural one • The regenerate signal, when the sample has been zeroed its natural TL by heating and then given an artificial radiation dose The last two glow curves allow to measure the sensitivity of a sample to natural radiations and are used to determine the paleodose.
There are several ways to determine the paleodose comparing the results of the different glow curves measured.The accumulation of trapped electrons, and the gaps left behind in the spaces they vacated, occurs at a measurable rate proportional to the radiation received from a specimen’s immediate environment.