Resonance Ionization Mass Spectrometry of Solar and Stellar Abundances

This work discusses techniques for determining elemental abundances of solar wind and isotopic abundances in presolar grains using resonance ionization mass spectrometry (RIMS), with particular attention paid to removing sample contamination prior to analysis. A cleaning procedure to remove terrestrial contamination from Genesis (solar wind) sapphire samples was employed with success in significantly reducing the surface coverage of Si-based melts. Sample preparation techniques for the front-side analysis of Genesis sapphire samples with the Chicago Instrument for Laser Ionization (CHILI) were also devised. A presolar grain separation procedure was developed, the Modified Chicago Method, with the intent to reduce contamination from solvents while maximizing the extraction of mineral and presolar grain types from meteorites. Compact fragments, spinel, hibonite, corundum, nanodiamonds, presolar graphite, and presolar SiC grains were separated from ~23 grams of CM2 meteorite Aguas Zarcas. Approximately 1700 presolar SiC candidate grains have been identified at the time of writing. Of these, 176 have been analyzed for light element isotopes (C, N, Si) with NanoSIMS, while 93 have been analyzed for heavy element isotopes (Mo, Ba, and Zr or Ru) with CHILI. The isotopic signatures for grains analyzed in this work are consistent with those of prior studies. Many grains show s-process enrichments in all of the analyzed elements, with varying degrees of mixing between the s-process and solar endmembers. Contamination in the form of IOM is present on some of the presolar SiC grain mounts and shows terrestrial Mo and Ba signal, but not Ru and Zr. Simultaneous analysis of more than one element with CHILI enables some conclusions to be drawn about contamination of grains, and the AZ SiC grains show slight Mo contamination.