ABSTRACT

We report Raman spectroscopic results of four density-separated fractions of a floating fraction (material similar to HF-HCl residues enriched in heavy noble gases) of the Allende meteorite. The Raman analyses were performed at two laser powers of 0.5 mW and 2-6 mW with the excitation wavelength of 532 nm. The typical Raman spectra of carbon were observed for all the samples, but these carbonaceous materials were very sensitive to the laser power at the analysis. The Raman parameters except for the intensity ratio of D band and G band are similar in all the fractions at the low laser power, but they changed at the high laser power in a different manner, probably due to the different degree of laser-induced heating. Our findings are that phase Q (the carrier of noble gas of the normal isotopic composition in meteorites) is enriched in the graphitic carbon having larger domain size compared to the major carbon in Allende and that this carbon is most affected by the laser heating.