We investigate the sputtering and ionization process that takes place during secondary ion mass spectrometry (SIMS) analysis in order to develop a better understanding of the underlying controls on elemental and molecular oxide secondary ion yields. Using data from a suite of uranium compounds that were sputtered with an O- primary beam on a NanoSIMS 50L, our goal is to understand whether a compound’s intrinsic properties, or processes operating at the sputtering site, exert the greatest influence over the relative abundances of uranium elemental and molecular oxide secondary ions observed during an analysis. While the observed ²³⁸U/²³⁸U¹⁶O and ²³⁸U/²³⁸U¹⁶O₂ of the various compounds exhibit considerable overlap, there are relationships between the weighted mean ²³⁸U/²³⁸U¹⁶O and ²³⁸U/²³⁸U¹⁶O₂ ratios for the various compounds and their enthalpies of formation. This reinforces the existing theory that the nature of the material being sputtered can influence relative ion yields (e.g. the SIMS matrix effect), but we also document significant evidence for the influence of processes operating at the sputtering site as a major factor. The existence of a strong relationship between the relative uranium molecular oxide production rate and the mass fractionation regimes taking place within an analysis, as well as the existence of sudden shifts in molecular oxide production rates taking place within an analysis, provide further evidence for the importance of processes related to the sputtering and ionization dynamics as exerting the most control over observed ion yields. Evaluation of our data within the context of existing models for secondary ion production during SIMS analysis highlights the need for additional models that consider the competing influences of a sample’s chemical and/or structural form, reactions taking place at the sputtering site, as well as the ionization and ion extraction dynamics of the various elemental and molecular oxide species.

我们研究了二次离子质谱 (SIMS) 分析过程中发生的溅射和电离过程，以便更好地了解对元素和分子氧化物二次离子产率的潜在控制。使用在 NanoSIMS 50L 上用 O-初级束溅射的一组铀化合物的数据，我们的目标是了解化合物的固有特性或在溅射现场运行的过程是否对铀的相对丰度产生最大影响。在分析过程中观察到的铀元素和分子氧化物二次离子。而观察到的²³⁸ U/ ²³⁸ U ¹⁶ O 和²³⁸ U/ ²³⁸ U ¹⁶ O ₂的各种化合物表现出相当大的重叠，加权平均值²³⁸ U/ ²³⁸ U ¹⁶ O 和²³⁸ U/ ²³⁸ U ¹⁶ O ₂之间存在关系各种化合物的比率及其形成焓。这强化了现有理论，即被溅射材料的性质会影响相对离子产率（例如 SIMS 基质效应），但我们也记录了重要证据，证明在溅射现场操作的工艺影响是主要因素。相对铀分子氧化物生产率与分析中发生的质量分馏机制之间存在很强的关系，以及分析中分子氧化物生产率的突然变化的存在，为重要性提供了进一步的证据与溅射和电离动力学相关的过程对观察到的离子产率施加最大的控制。