Positron Spectroscopy of Surfaces

****非技术摘要****该项目将采用新的实验和理论方法来获取有关表面的独特信息，这些信息可用于开发用于太阳能转换，制氢和储能的改进材料。新的表面分析方法将在材料的最上层原子层中利用正电子（电子的反物质当量）与原子中的电子湮灭所产生的伽马射线信号进行研究。由于伽马射线可以很容易地穿透气体和固体，因此可以探测多孔材料、粗糙的技术表面和颗粒状材料的内外表面的化学相互作用。利用新的光谱与正电子湮灭过程的理论建模相结合进行的实验可以预期产生关于原子和分子与表面相互作用的关键新知识，这些知识是使用其他方法无法获得的，并且将具有广泛的科学和工业影响。该项目将为研究生和本科生提供广泛的机会来设计、构建和实施新的实验和理论资源，并将这些资源用于前沿研究，在具有重大技术和科学重要性的领域给予宝贵的研究培训。该奖项得到了材料研究部、化学部以及化学、生物工程和环境运输系统部的支持。****技术摘要****该项目将利用一束低能量正电子进行实验，结合第一性原理计算，研究正电子与表面的基本相互作用，并利用湮灭伽马谱获得的元素特定信息开发表面分析的新方法。新的光谱将产生具有顶级原子层特异性的表面特定化学信息。伽马射线的穿透性将使探测多孔材料、粗糙的技术表面和颗粒状材料的内部表面成为可能。新的光谱将与纳米结构表面湮灭概率的第一性原理理论建模相结合，研究催化和光催化中的重要问题，包括纳米结构表面的电荷转移以及催化和光催化系统中活性位点的性质。该项目预计将导致重要的新的原位表面分析方法的发展，并产生关于原子和分子与表面相互作用的关键新知识。该项目将为表面和界面科学研究前沿的博士和本科生提供培训。该奖项得到了材料研究部、化学部以及化学、生物工程和环境运输系统部的支持。

****NON-TECHNICAL ABSTRACT****This project will employ new experimental and theoretical methods to obtain unique information about surfaces that can be used to develop improved materials for use in solar energy conversion, hydrogen generation and energy storage. The new surface analytic methods will make use of the gamma-ray signals arising from the annihilation of positrons (the antimatter equivalent of the electron) with electrons in atoms in the topmost atomic layer of the materials studies. Because the gamma-rays can easily penetrate through gases and solids it will be possible to probe chemical interactions at both external and internal surfaces of porous materials, rough technical surfaces, and granular materials. Experiments carried out using the new spectroscopies combined with theoretical modeling of positron annihilation processes can be expected to yield critical new knowledge about the interaction of atoms and molecules with surfaces that cannot be obtained using other methods and that will have broad scientific and industrial impact. This project will provide extensive opportunities for graduate and undergraduate students to design, build and implement new experimental and theoretical resources and to employ these resources in cutting edge research giving them invaluable research training in areas of great technological and scientific importance. This award receives support from the Division of Materials Research, the Division of Chemistry, and the Division of Chemical, Bioengineering, and Environmental Transport Systems.****TECHNICAL ABSTRACT****This project will employ experiments utilizing a beam of low energy positrons in combination with first principles calculations in studies aimed at understanding fundamental interactions of positrons with surfaces and at the development of new methods for surface analysis using element specific information obtained from annihilation gamma spectra. The new spectroscopies will yield surface specific chemical information with top atomic layer specificity. The penetrating nature of the gamma rays will make it possible to probe internal surfaces in porous materials, rough technical surfaces, and granular materials. The new spectroscopies will be combined with first principles theoretical modeling of annihilation probabilities on nano-structured surfaces to study important questions in catalysis and photo-catalysis including charge transfer at the surface of nanostructures and the nature of active sites in catalytic and photo-catalytic systems. This project is anticipated to lead to the development of important new in-situ methods of surface analysis and to yield critical new knowledge about the interaction of atoms and molecules with surfaces. The project will provide training for Ph.D. and undergraduate students at the forefront of research in surface and interface science. This award receives support from the Division of Materials Research, the Division of Chemistry, and the Division of Chemical, Bioengineering, and Environmental Transport Systems.