Positron Spectroscopy of Surfaces

* 非技术摘要 * 本项目将采用新的实验和理论方法，以获得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利用正电子（电子的反物质等价物）与材料研究最顶层原子层中原子中的电子湮灭产生的伽马射线信号。 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、粗糙技术表面和颗粒材料的内外表面的化学相互作用。 使用新的光谱学结合正电子湮灭过程的理论建模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，这些知识无法使用其他方法获得，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，设计，构建和实施新的实验和理论资源，并在前沿研究中使用这些资源，使他们在具有重要技术和科学意义的领域获得宝贵的研究培训。 该奖项得到了材料研究部，化学部和化学，生物工程和环境运输系统部的支持。技术摘要 * 该项目将采用利用低能正电子束的实验，并结合第一原理计算，以了解正电子与表面的基本相互作用，并利用从湮灭伽马谱中获得的元素特定信息开发新的表面分析方法。 新的光谱学将产生具有最高原子层特异性的表面特异性化学信息。 伽马射线的穿透性质将使探测多孔材料、粗糙技术表面和颗粒材料的内表面成为可能。 新的光谱学将与纳米结构表面湮灭概率的第一原理理论模型相结合，以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。 预计该项目将导致开发重要的新的表面分析原位方法，并产生关于原子和分子与表面相互作用的重要新知识。 该项目将为博士提供培训。以及处于表面和界面科学研究前沿的本科生。该奖项得到了材料研究部，化学部和化学，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.