Speaker
Description
Primitive meteorites contain nanometer- to micrometer-sized grains that exhibit isotopic anomalies in various elements relative to the solar system composition. These grains, known as presolar grains, preserve isotopic signatures that reflect nucleosynthesis in the stellar sources before the formation of the solar system. High-precision trace element isotopic analyses of presolar grains provide such information, allowing comparisons with predictions from nuclear physics and stellar evolution models. Among the presolar grains, presolar SiC grains have been extensively studied because they are relatively abundant in meteorites, and well-established methods exist for their isolation. However, because of their small size, high spatial resolution is required to analyze individual grains. In addition, high sensitivity is needed to obtain sufficient precision. Therefore, in this study, we employ a laser post-ionization secondary neutral mass spectrometer (SNMS) developed at the University of Osaka. The high spatial resolution of the Ga ion beam and the high ion yield achieved by laser post-ionization make this technique promising for isotopic analysis of presolar SiC. A multi-turn time-of-flight mass spectrometer (MULTUM) is used for mass separation, providing high mass-resolving power by adjusting the number of cycles.
In this study, we focused on Ti, a relatively abundant trace element in presolar SiC. Through instrument optimization and improvement of the measurement conditions, we successfully performed Ti isotopic analyses of presolar SiC. Ti isotopic anomalies were detected, and the observed isotopic patterns demonstrated precision comparable to that of previous studies. In the future, we plan to extend the method to simultaneous analyses of Ti and heavy elements, providing stronger constraints on the physical conditions of the parent stars.
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