Milling-Induced Reset of Thermoluminescence and Deformation of Hydroxyl Species in the Near-Surface Layers of Quartz Grains

Reset mechanisms of thermoluminescence (TL) signals in the near-surface layers (~500 nm thick) of quartz grains during milling are discussed on the basis of the dependence of TL glow-curves and infrared absorption spectra on grain diameter. TL measurements (heating to 370°C at 1°C/s) indicate that the near-surface layer does not seem to emit TL at ~250-400°C, especially in the blue range, even in TL measurements after re-irradiation. In contrast, the layer seems to emit more TL at ~130°C than the inner original quartz. On the other hand, diffused reflection infrared Fourier transform spectrometry indicates that hydroxyl species (e.g. Al-OH, Li-dependent OH and molecular H₂O species) are deformed in the near-surface layer. These two series of data suggest that TL recombination sites in the near-surface layer are deformed or broken during milling and contribute to TL emission unusually strongly.