| Popis: |
The thermoluminescence from a French limestone shows peaks in the glow curve at 142±11, 164±14, 194±11, 286±10 and 360±10°C measured at a heating rate of 5.2°C s−1. The bleaching and phototransfer properties of these peaks are presented for bleaching times in a solar simulator extending up to 2 weeks. The height of the principal peak in the glow curve at 286°C declines exponentially with bleaching time over the first 10 min and then over the following 2 weeks declines in proportion to t−0.34±(0.01), where t is the bleaching time. The peak at 360°C is bleached exponentially with time over a period of 60 min and thereafter shows no detectable change in intensity. The phototransferred thermoluminescence rises to a maximum at 4 min of exposure in the solar simulator and thereafter for 2 weeks falls proportionally to t−0.32±(0.02), where t is the exposure time. The wavelength dependence of the bleaching of the principal 286°C peak in the natural thermoluminescence glow curve was investigated over the wavelength range 340–750 nm, obtained using optical filters and the solar simulator. The 340–400 nm region was found to be of most importance for bleaching, while wavelengths longer than 500 nm had little influence. |
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