Characterization of artificially shocked forsterites : (2) Profile analysis of photo-luminescence spectra
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Synthetic single crystals of forsterite shocked up to 82.0GPa have been examined by the profile analysis of photo-luminescence spectra. The forsterites give rise eight broad bands in photo-luminescence spectra in contrast to unshocked forsterite having usually faint and obscure luminescence. Their intensity increases linearly with increasing the pressure up to 46.2GPa, while over the pressure the intensity abruptly decreases. The intensity variation also has a close relationship to Raman band shift and broadening, implying the variable degree of lattice deformation in shocked forsterites. The critical shock pressure of 46.2 GPa nearly corresponds to the onset shock pressure of phase transition (50GPa) on the Hugoniot curve of forsterite (Syono <I>et al.</I>, 1981). Luminescence mechanism in the shocked forsterite may be the emission transition between the deformed electron levels with vibrational sub-levels in its [SiO<SUB>4</SUB>]<SUP>4−</SUP> molecular orbitals. This is a new type of photo-luminescence in silicate minerals that can be called as the deformation luminescence.<BR>The correlation between the intensity of photo-luminescence and shock pressure loaded on the forsterites is formulated, and applied to estimate the shock pressure of Dhurmsala LL6 chondrite; it ranges from 26 to 29 GPa.
- Mineralogical Journal
Mineralogical Journal 21(3), 119-130, 1999-07-01
Japan Association of Mineralogical Sciences