This proposal seeks funding of $60K for partial purchase of a femtosecond laser ablation system (fsLA) to be used as an sample introduction system on an existing multi-collector ICP-MS system within the Radiogenic Isotope Laboratory at UW-Madison. The University will contribute $355K and NASA will contribute $60K toward the purchase. Isotope measurements may be improved by shorter wavelength, faster pulse-width laser ablation systems. Systems with wavelengths in the deep UV and femtosecond pulse widths are beginning to be fielded in the geoscience community. Recent studies show radiogenic isotopes ratios with elements like Sr, Pb and Hf are better preserved from source material when ablated using fsLA. The prime goal for initial experiments is measuring Fe isotopes in individual carbonates produced by microbial Fe3+ reduction. The fsLA system will be necessary to tease out Fe fractionation factors which would not possible with bulk analyses. Measurements with bulk carbonates is particularly challenging because Fe isotopes tend to fractionate during dissolution. The effect is noticeable when sequential acid digestions are performed. The fsLA system should allow individual carbonates to be analyzed mitigating this bias. The PIs present considerable evidence to support the fsLA system over microprobe or SIMS analyses. Combination analysis with both SIMS and fsLA is suggested. The fsLA system will offer a wide range of analytical possibilities to UW-M. Students and post-docs will be able to utilize the system. While Fe isotopes will be initial focus, sedimentary and igneous geochemistry will benefit from shorter pulse laser ablation. Zircon U-Pb and Hf analyses will be possible. Collaborative efforts with the Rare Gas Laboratory at UW-M will also be evident.
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