When ionising radiation (predominantly alpha -, beta - or gamma -radiation) interacts with an insulating crystal lattice (such as quartz or feldspar), a net redistribution of electronic charge takes place. Electrons are stripped from the outer shells of atoms and though most return immediately, a proportion escape and become trapped at ‘meta-stable' sites within the lattice. The net charge redistribution continues for the duration of the exposure and the amount of trapped charge is therefore related to both the duration and intensity of radiation exposure (ignoring saturation effects).

Even though trapped at meta-stable sites, electrons become ‘free' once again under certain conditions (if the crystal is heated and, for some trapping sites, if illuminated). Once liberated a free electron may become trapped once again or may return to a vacant position left by the absence of a previously displaced electron (a ‘hole'). This latter occurrence is termed ‘recombination' and the location of the hole is described as the ‘recombination centre'. As recombination occurs, a proportion of the energy of the electron is dissipated. Depending upon the nature of the centre where recombination occurs, this energy is expelled as heat and/or light. When the crystal grain is either heated or illuminated following irradiation (the ‘dose') the total amount of light emitted is therefore related to the number of liberated electrons and available recombination sites. This is the fundamental principle upon which luminescence dating is based, namely that when stimulated (either with light or heat) the amount of light emitted by the crystal sample is related to the total absorbed radiation dose (up to the level of signal saturation).

During the event to be dated, for example when sediment transport occurs, individual crystals are exposed to natural daylight and the trapped charge that accumulated during burial is removed (i.e. the light ‘frees' the trapped electron population, as described above) - termed ‘re-setting', ‘zeroing' or ‘bleaching' of the signal. On subsequent deposition and burial the crystal grains are once again returned to darkness and trapped charge accumulation proceeds as before. Re-setting of the signal is achieved by heating in the case of pottery. In cases where the duration of dosing (since the last resetting event) is not known, as for dating, estimates can be made from laboratory measurements. The response (the sensitivity) of the sample to radiation dose (i.e. the amount of light observed for a given amount of radiation, usually ß -radiation) must be established. This is termed the ‘dose response curve' or ‘growth curve'. From this relationship the equivalent (in most cases ß -) radiation exposure required to reproduce the light level observed following the environmental dose can be estimated. This estimation is called the ‘equivalent dose' (De). The De is therefore an estimate of the total dose absorbed during the last burial period (assuming full re-setting prior to burial). If the ‘dose rate' (the amount of radiation per unit time administered during burial) is known, the duration of the dosing period (the burial age) can be calculated:

Age (years) = De (Gy) / dose rate (Gy per year).