TUNNEL AFTERGLOW, FADING AND INFRARED-EMISSION IN THERMOLUMINESCENCE OF FELDSPARS

Anomalous fading of TL, OSL and IRSL has been observed in many samples of feldspars and attributed to the tunnel effect. Investigations do s how expected tunnel afterglow except for samples with no fading. Its i ntensity, quite noticeable at LNT, is in proportion with reported rate of fading. The emission is entirely in the red and infrared part of t he spectrum. An important thermal quenching is observed. Low temperatu re storage results in fading of TL. Cathodoluminescence emission spect ra, monitored from 200 to 900 nm, do confirm TL observations. They sho w two well-separated ranges: one, ''blue'', from UV to yellow (the onl y one observed in usual TL dating), displays various emission bands; t he other, ''IR'', red and infrared, shows a well-characterized narrow Gaussian emission band, with a maximum around 720 nm. Models are propo sed, relating fading with disorder in crystals. Tunnel afterglow appea rs as a good criterion of fading in feldspars.