Research in Secondary Ion and Neutral Mass Spectrometry

在由分析和表面化学项目支持的研究中，Emile Schweikert教授和他在德州农工大学的同事正在开发表面质谱分析的新方法。该研究的重点是从keV单原子和多原子弹丸轰击表面时产生的弹射物中提取更多信息。一个目标是通过检测巧合发射的二次离子来实现纳米相表征。该方法依赖于“质量分离飞行时间质谱法”的新概念。第二个目标是提高检测灵敏度，这转化为检测中性点的要求。该方法是在环境压力下对解吸的中性物进行碰撞冷却，将它们收集到一个超音速分子束中，并对它们进行高效的高温电离，以便随后通过飞行时间质谱法进行鉴定。除了提高检测灵敏度外，该方法还可用于不易在真空中检测的表面。该项目涉及用于检测表面的先进化学分析专业知识。以纳米结构为重点的表面科学和技术的进步要求对微小分子的检测。这项研究旨在提高我们识别纳米结构的化学组成和检测分散在表面上的少量分子的能力。这项工作将集中在两种新的质谱分析方法上。一种基于“质量分离飞行时间质谱法”的技术有望对小至~ 30nm的纳米结构域进行化学分析。另一种方法涉及“环境压力二次中性质谱法”，其目标是检测分子在表面上随机分布（而不是在纳米结构中组装）的时间，以及当前技术无法检测到的数量。

In research supported by the Analytical and Surface Chemistry Program, Professor Emile Schweikert and his coworkers at Texas A&M University are developing new methods for mass spectrometry of surfaces.The research focuses on extracting more information from the ejecta generated when bombarding surfaces with keV mono and polyatomic projectiles. One objective is to achieve nanophase characterization via the detection of coincidentally emitted secondary ions. The approach relies on the novel concept of "mass separated time-of-flight mass spectrometry". A second objective is to advance detection sensitivity, which translates into the requirement of detecting neutrals. The approach is to collisionally cool the desorbed neutrals at ambient pressure, collect them into a supersonic molecular beam and subject them to efficient hyperthermal ionization for subsequent identification by time-of-flight mass spectrometry. In addition to enhanced detection sensitivity, the procedure should be useful for surfaces not readily amenable to examination in vacuum.This project deals with advancing chemical analysis expertise for examining surfaces. Progress in surface science and technology with emphasis on nanostructures requires the detection of vanishingly small amounts of molecules. The research aims to enhance our capabilities for identifying the chemical makeup of nanostructures and for detecting small numbers of molecules dispersed on a surface. The work will focus on two novel methods of mass spectrometry. One based on "mass-separated time-of-flight mass spectrometry" is expected to enable chemical analysis of nanodomains as small as ~ 30 nm. The other involves "ambient pressure secondary neutral mass spectrometry" with the goal of detecting molecules when they are randomly distributed on a surface (rather than assembled in a nanostructure) and when they are present in amounts which cannot be detected with current techniques.