6:15 PM - 7:30 PM
[PPS22-P01] Development on the post-ionization SNMS and application for the isotopic measurement of Presolar SiC grains
Keywords:SIMS, presolar grain, in-situ analysis, isotope anomaly, nuclear synthesis, meteorite
Here, we report on the development on the post-ionization Sputtered Neutral Mass Spectrometry (SNMS) and an application for the isotopic measurement of presolar silicon carbide grains (SiCs). In this analytical system, the neutrals particles sputtered by Ga ion beam of which diameter is 40nm~2 μm was post-ionized by femt-second laser, and separated by the multi-turn time-of-flight mass spectrometer ‘MULTUM’ depending on their masses. Last year, we has achieved the about 1000 times higher secondary ion yield for Pb signals with high mass resolution (Nakabayashi et al. 2014).
Based on the preliminary Si isotope analysis using SNMS, we confirmed that current SNMS system shows good reproducibility of terrestrial Si isotopic ratios and figured out that the instrumental mass fractionation is -150~200‰/amu. Moreover, we successfully separate 28Si (=27.977 amu) and 29Si (=28.976 amu) peaks from interference peaks such as N2 (=28.006 amu), CO (=27.995 amu) and 28SiH (=28.985 amu) by using MULTUM. Finally, we also confirm the heavy isotopic anomaly of Si isotopes (δ30Si/28Si=100~200‰ ,δ29Si/28Si=130~200‰) of presolar SiC candidates extracted from Murchison meteorite, which are consistent with those of previous studies.