Analytical Method Development: Comparison of Elemental and Isotopic Fractionation During Femtosecond and Nanosecond Laser Ablation

同位素和化学成分的原位分析对于记录地质样品的空间非均质性至关重要，现在通常通过激光烧蚀方法完成。激光技术的改进是目前地球化学界的兴趣所在，相对较新的技术的潜在优势已经显示出一些成长的痛苦，但前景广阔。该合同允许研究人员通过比较两种关键的激光烧蚀系统，评估使用新型激光烧蚀技术对主要元素进行高精度稳定同位素分析所需的方法。该研究将集中在铁同位素上，以严格测试质量偏差问题，其结果可以扩展到其他同位素系统。铁也是大多数造岩矿物中存在的主要元素，因此它将引起地球化学界的广泛兴趣。研究结果将为不同原位分析方法的实验室间比较提供依据。该奖项将为涉及激光消融的物理学博士后提供培训和专业知识。该奖项资助了使用激光烧蚀（LA）对主要元素进行高精度稳定同位素分析的技术开发，并比较飞秒(fs)-与纳秒(ns)-LA技术，以了解烧蚀和电离过程中同位素分馏的潜在过程。由于在相关尺度上已知的同位素非均质性，将对fs-和ns-LA用于铁同位素分析的准确性进行评估。该结果将适用于其他稳定同位素系统，如镁、硅和钙，并应扩展到与fs-LA和ns-LA相关的质量偏差问题的放射性成因同位素系统。具体的研究目标是评估fs-LA无基质效应的程度，并确定与ns-LA和标准溶液雾化方法相比，fs-LA的哪些具体方面似乎产生了无基质分析。该研究将致力于测量fs-和ns-LA产生的气溶胶的粒度分布、化学和同位素组成以及形态特征（例如，团块和球状体）。此外，基质效应将通过使用矿物组同位素标准（例如，矿物如铁铁矿、铁白云石、铁白云石）和通过向LA气溶胶流中添加元素来表征。在溶蚀雾化器产生的气溶胶中。

In-situ analyses of isotopic and chemical composition are critical for documenting spatial heterogeneities within geological samples, and are now commonly accomplished by laser ablation methods. Improvements in laser technology are of current interest to the geochemical community and the potential advantages of relatively new technology has shown some growing pains but holds great promise. This award allows the researchers to evaluate the approaches needed for high-precision stable isotope analysis of major elements using new laser ablation technology by comparing two key laser ablation systems. The research will focus on iron isotopes to rigorously test issues of mass bias, the results of which can be extended to other isotope systems. Iron is also a major element that occurs in most rock-forming minerals, and so it will be of widespread interest to the geochemical community. The results will provide a basis for inter-laboratory comparisons of different methods of in situ analysis. The award will provide training and expertise for a postdoctoral fellow on the physics involved in laser ablation.This award funds the development of techniques for the high-precision stable isotope analysis of major elements using laser ablation (LA) and to compare femtosecond (fs)- vs. nanosecond (ns)-LA technologies to understand potential processes of isotopic fractionation during the ablation and ionization processes. The accuracy of fs- and ns-LA for isotopic analysis of iron isotopes will be evaluated due to known isotope heterogeneities at relevant scales. The results will be applicable to other stable isotope systems such as magnesium, silicon, and calcium, and should be extendable to radiogenic isotope systems in terms of mass bias issues associated with fs-LA and ns-LA. The specific research goals are targeted to evaluate the degree to which fs-LA is free of matrix effects and to determine what specific aspects of fs-LA appear to generate matrix free analysis as compared to ns-LA and standard solution nebulization methods. The study will be devoted to measuring the particle size distribution, chemical and isotopic composition, and morphological characteristics (e.g., agglomerates and spheroids) of aerosols generated by both fs- and ns-LA. Moreover, matrix effects will be characterized by using mineral group isotope standards (e.g., minerals such as siderite, ankerite, ferroan dolomite) and addition of elements into the LA aerosol stream by ?teeing? in the aerosol produced from a desolvating nebulizer.