Positron Annihilation Induced Auger Electron Spectroscopy

Weiss正电子湮灭诱导俄歇电子能谱（PAES）采用了一种全新的过程，其中俄歇能谱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通过碰撞电离产生的。由于正电子在湮灭前在表面外的成像势阱中被捕获，PAES对固体最上层原子层的临界层具有独特的敏感性。本文提出的实验将利用PAES的这种能力来确定最顶层原子层的元素含量，从而了解具有重要催化作用的超薄金属薄膜系统，包括铜上的钕和钯上的铜，以及研究铂-镍和铂-金等合金的表面偏析。事实上，PAES测量可以使用比传统俄歇技术所需的能量剂量少许多数量级的能量剂量，这将用于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）利用了一种全新的过程，在这种过程中，从固体中发射所谓的俄歇电子所需的输入能量来自原子核中正电子（反物质）与负电子的湮灭，而不是像传统的俄歇方法那样来自高能入射电子与核心电子的碰撞。PAES对固体最上层原子层的组成非常敏感，因为正电子在湮灭之前就在表面外被捕获。拟议的实验将利用PAES的这种灵敏度来确定最上层原子层的元素含量，以推进对催化重要的超薄膜材料的理解，如钯上的铜，并研究合金中组成元素的表面偏析，如铂镍。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，这一事实将用于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。＊＊＊

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. ***