TUNNELING AFTERGLOW AND POINT-DEFECTS IN FELDSPARS

The recent development of the infrared stimulated luminescence (OSL) o f feldspars enhanced their importance for geological dating in the las t 100 000 years. Unfortunately this application is hindered by the phe nomenon of anomalous fading of their thermoluminescence (TL) and OSL, attributed to tunnel effect between (D-A) pairs. In the case of feldsp ars, this fading is very frequent and so far unpredictable. A systemat ic comparative study of the tunnel effect in afterglow of irradiated f eldspars has been made on a collection of some well caracterised 32 di fferent samples of feldspar crystals. All of them display a low temper ature afterglow due to tunnel effect in a gaussian near-infrared band centered on 710 nm. It is attributed to Fe3(+) ions involved with the so-called phenomenon of 'Al-Si order-disorder' in occupation of sites in the feldspar lattice. This effect is known classically in mineralog y and crystallography of feldspars, but had not been related to tunnel luminescence so far. This tunnel afterglow constitutes an easy criter ion of TL datability of feldspars.