Positron Annihilation Induced Auger Electron Spectroscopy

正电子湮没诱导俄歇电子能谱

• 批准号: 9502459
• 负责人: Alex Weiss
• 金额: $ 27.79万
• 依托单位: University of Texas at Arlington
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-06-01 至 1999-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9502459&HistoricalAwards=false
• 关键词: Positron; Annihilation; Induced; Auger; Electron

9502459 Weiss Positron annihilation induced Auger Electron Spectroscopy (PAES) utilizes a fundamentally new process in which the excitations necessary for Auger spectroscopy are created by positrons annihilating core electrons and not, as in conventional Auger methods, by collisional ionization. PAES is uniquely sensitive to the critical topmost atomic layer of solids due to the trapping of positrons in an image potential well just outside the surface before annihilation. Experiments are proposed which will capitalize on this ability of PAES to determine the elemental content of the topmost atomic layer in achieving an understanding of catalytically important ultrathin metal fillm systems, including neodynium on copper, and copper on palladium, as well as to study surface segregation in alloys such as platinum- nickle and platinum-gold. The fact that PAES measurements can be made using energy doses many orders of magnitude less than those needed with conventional Auger techniques will be utilized to study fragile adsorbed layers and chemically unstable systems including hydrogen and organic molecules on metal surfaces. %%% Positron annihilation induced Auger Electron Spectroscopy (PAES) utilizes a fundamentally new process in which the input energy required for the emission of so-called Auger electrons from a solid results from the annihilation of positive electrons (antimatter) with negative electrols in atomic cores rather than from collisions of energetic incident electrons with the core electrons, as in conventional Auger methods. PAES is uniquely sensitive to the composition of the critical topmost atomic layer of solids due to the trapping of positrons just outside the surface before annihilation. The proposed experiments will capitalize on this sensitivity of PAES to determine the elemental content of the topmost atomic layer to advance undertanding of catalytically important ultrathin film materials, such as copper on palladium, and to study the surface segregation of constituent elements in alloys such as platinum-nickel. In addition, the fact that PAES measurements can be made using energy doses hundereds of times weaker than those needed with conventional Auger methods will be utilized to study fragile adsorbed layers and chemically unstable coverings such as hydrogen and organic molecules on metal surfaces. ***

9502459韦斯正电子湮没诱导俄歇电子能谱（PAES）利用 一种全新的过程，其中俄歇光谱学所需的激发是由正电子湮灭核心电子产生的，而不是像传统的俄歇方法那样， 碰撞电离。PAES对固体的临界最顶层原子层非常敏感，因为在湮灭之前，正电子被捕获在表面外的图像势阱中。 提出了实验，其将利用PAES的这种能力来确定最顶层原子层的元素含量，以实现对催化重要的非金属填充系统的理解，包括在铜上的钕和在钯上的铜，以及研究诸如铂-镍和铂-金的合金中的表面偏析。事实上，PAES测量可以使用的能量剂量比传统的俄歇技术所需的低许多数量级，将被用来研究脆弱的吸附层和化学不稳定的系统，包括金属表面上的氢和有机分子。 正电子湮灭诱导俄歇电子能谱（PAES）利用一种全新的过程，其中从固体发射所谓俄歇电子所需的输入能量来自正电子（反物质）与原子核中的负电子的湮灭，而不是来自高能电子的碰撞。 入射电子与核心电子， 作为 在常规俄歇方法中。 PAES对固体的临界最顶层原子层的组成非常敏感，因为在湮灭之前正电子会被捕获在表面之外。 拟议的实验将利用PAES的这种灵敏度来确定最顶层原子层的元素含量，以推进 了解 重要催化剂 薄膜材料，如钯上的铜，并研究合金，如铂镍合金中的组成元素的表面偏析。 此外，PAES测量可以使用比传统俄歇方法所需的能量剂量弱数百倍的能量剂量进行，这一事实将被用来研究脆弱的吸附层和化学不稳定的覆盖物，如金属表面上的氢和有机分子。 ***