Barium isotopes in individual presolar silicon carbide grains from the Murchison meteorite

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作者：

MR Savina，AM Davis，CE Tripa，MJ Pellin，RN Clayton，RS Lewis，S Amari，R Gallino，M Lugaro

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摘要：

Barium isotopic compositions of single 2.3–5.3 μm presolar SiC grains from the Murchison meteorite were measured by resonant ionization mass spectrometry. Mainstream SiC grains are enriched in s-process barium and show a spread in isotopic composition from solar to dominantly s-process. In the relatively coarse grain size fraction analyzed, there are large grain-to-grain variations of barium isotopic composition. Comparison of single grain data with models of nucleosynthesis in asymptotic giant branch (AGB) stars indicates that the grains most likely come from low mass carbon-rich AGB stars (1.5 to 3 solar masses) of about solar metallicity and with approximately solar initial proportions of r- and s-process isotopes. Measurements of single grains imply a wide variety of neutron-to-seed ratios, in agreement with previous measurements of strontium, zirconium and molybdenum isotopic compositions of single presolar SiC grains.

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关键词：

Bibliography, Experimental/ barium grain size isotope relative abundance meteorites silicon compounds/ barium isotopes presolar silicon carbide grains Murchison meteorite presolar SiC grains mainstream SiC grains resonant ionization mass spectrometry s-process barium grain size barium isotopic composition nucleosynthesis asymptotic giant branch stars solar initial proportion neutron strontium zirconium molybdenum isotopic compositions 2.3 to 5.3 micron SiC Ba/ A9650M Meteorites, micrometeorites A9635E Planetary chemical composition/ size 2.3E-06 to 5.3E-06 m/ SiC/bin Si /bin C/bin Ba/el