[SMP33-P01] Raman spectroscopy of seifertite
Keywords:Seifertite, Raman spectroscopy, Meteorite
Seifertite in silica grains of synthetic samples and lunar (NWA 4734) and martian meteorites (Zagami, NWA 2975) were identifications by a synchrotron XRD analysis at Spring-8 BL-10 and were employed for Raman spectroscopy. Seifertite were synthetized from synthetic cristobalite powders using multi-anvil press at 16 GPa, 673 K and 0.5 hour. Raman spectroscopy were performed for synthetic and meteoritic silica grains using Nd: YAG 532 nm at 20 mW for 3 minutes exposure time.
Raman spectra of synthetic seifertite have pronounced peaks at 380, 515, 564, 739 and 796 cm−1 and weak peaks at 401, 496, 539, 547, 606 and 749 cm−1. Similar Raman signature was obtained from seifertite in lunar and martian meteorites. These Raman shifts and relative intensities are well corresponding to the values calculated within the density-functional perturbation theory for seifertite. Based on the calculation, thee Raman peaks at 380, 515, 564, and 796 cm−1 are assigned to Ag, those at 401, 496, and 539 cm−1 to B1g, 606 and 749 cm−1 to B2g, and 547 and 739 cm−1 to B3g modes. After laser beam irradiation for 30 minutes, the distinct Raman signature can be detected from synthetic and meteoritic seifertite. Therefore, Raman spectroscopy enables determination of the structure and identification of SiO2 polymorphs with high-spatial resolution and without destruction.