Research in Secondary Ion and Neutral Mass Spectrometry

在分析和表面化学项目的支持下，德克萨斯州A M大学的Emile Schweikert教授和他的同事正在开发表面质谱的新方法。研究重点是从用keV单原子和多原子射弹轰击表面时产生的喷出物中提取更多信息。 一个目标是通过检测偶然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”的新概念。 第二个目标是提高探测灵敏度，这意味着需要探测中性粒子。 该方法是在环境压力下碰撞冷却脱附的中性物质，将它们收集到超声分子束中，并将它们进行有效的超热电离，以便随后通过飞行时间质谱进行鉴定。除了提高检测灵敏度外，该程序还可用于不容易在真空中检测的表面。本项目涉及用于检测表面的先进化学分析专业知识。 表面科学和技术的进展，重点是纳米结构需要检测到的消失少量的分子。 该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方法。 一种基于“质量分离飞行时间质谱法”的方法有望实现小至~ 30 nm的纳米结构域的化学分析。 另一个涉及“环境压力二次中性质谱”，其目标是检测分子随机分布在表面上（而不是组装在纳米结构中）时，以及当它们以当前技术无法检测到的量存在时。

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.