Positron Spectroscopy of Surfaces

University Of Texas At Arlington, Arlington TX

Investigators

Abstract

****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.