Positron Annihilation Induced Auger Electron Spectroscopy

9502459 Weiss正电子湮没诱导俄歇电子能谱(PAES)利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没核心电子而不是像传统的俄歇方法那样通过碰撞电离产生的。PAES对固体最顶层的临界原子层特别敏感，这是因为在湮灭之前，正电子在表面外的镜像势中被俘获。建议利用PAES的这一能力来确定最顶层原子层的元素含量，以了解具有催化作用的重要超薄金属填充系统，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。PAES测量可以使用比传统俄歇技术小许多个数量级的能量剂量进行测量，这一事实将被用于研究脆弱的吸附层和化学不稳定体系，包括金属表面上的氢和有机分子。正电子湮没诱导俄歇电子能谱(PAES)利用了一种全新的过程，在该过程中，从固体发射所谓的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，而不是像传统的俄歇方法那样来自高能入射电子与核电子的碰撞。由于正电子在湮灭前就被捕获在表面外，PAES对固体的关键最顶层原子层的组成是唯一敏感的。拟议的实验将利用PAES的这种敏感性来确定最顶层原子层的元素含量，以促进对催化重要的超薄膜材料(如铜在钯上)的了解，并研究组成元素在合金(如铂镍)中的表面偏析。此外，PAES测量可以使用比传统俄歇方法所需能量小数倍的能量剂量进行测量，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。***

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. ***