Abstract
An on-line spectrometry of several museum feldspar specimens showed two broad TL-emissions around 150-200°C, separable into a blue thermoluminescence (BTL, having a peak at 450 nm) covering 350-550 nm and a far-red TL (far-RTL, giving a peak at 710 nm) ranging 650-760 nm in wavelengths. TL-glowcurve shapes and the dose-response of TL sensitivity showed a certain dependency not only on the far-RTL or BTL-detection, but also on kinds of feldspar samples. Particularly, alkaline feldspars gave higher sensitivity in comparison with plagioclase with Ca-rich feldspar.
Concerning the albite as one kind of feldspar, the far-RTL showed negligibly small fading rate within a few percentages, whereas the BTL gave up to 18% reduction after the storage for 7 months at room temperature. The results revealed that the far-RTL source would be stable and preferable for the TL dating in spite of intrinsically weak intensity, estimated in the detective limitation in a few Gy, equivalent to archaeological burnt feldspar constituents approximately 1 000 years ago. Finally, a far-RTL emission mechanism was assigned to the participation of electric charge transfer on Fe2+ from Fe3+-impurity rather than the mechanism of energy transfer into Fe3+.
