Optically stimulated luminescence (OSL) study of synthetic stishovite

Optically stimulated luminescence (OSL) of synthetic stishovite was investi gated for a future dating technique of meteor impact craters. Luminescence around 330 nm was measured on the gamma -ray irradiated stishovite under tw o stimulating light sources of infrared laser (830 nm) and blue light emitt ing diode set (470 nm). Thermoluminescence (TL) studies before and after th e OSL measurements showed the intensities around 100-200 degreesC and 220-3 50 degreesC to increase and those around 350-450 degreesC to decrease. This indicates that a part of deep-trapped charges excited during the OSL measu rements were retrapped by shallower traps. The infrared stimulated luminesc ence (IRSL) after the TL measurement up to 450 degreesC could not be detect ed, while the blue light stimulated luminescence (BLSL) after TL had about one-tenth of the intensity before TL, This indicates that a part of the cha rges in shallower traps were detrapped thermally and returned to the deeper traps which were related to BLSL, The result implies that some of the BLSL -related traps are quite stable at room temperature and could be used for g eological dating. In addition, two paramagnetic centers produced by sudden release of high pressure in synthesis process were found in the unirradiate d stishovite by electron spin resonance (ESR). Their g-factors are g(parall el to) = 2.00181 and g(perpendicular to) = 2.00062 for an axial signal and g = 2.00305 for the other isotropic signal. These signals could be used for an evidence of impacts if those signals could be stored in geological time . (C) 2000 Elsevier Science Ltd. All rights reserved.