US-France Cooperative Research: Studies of Surface Melting in Crystalline Systems

该奖项将支持Jay Dash博士和Oscar Vilches博士与他们在华盛顿大学的学生，以及法国艾克斯-马赛大学的Michel Bienfait和Jean Suzanne教授在低温物理方面的合作研究。拟议项目的目标是开展晶体系统中表面熔化的研究。两个特别令人感兴趣的系统是二氧化氢-冰和厚厚的固体氢同位素物理吸附薄膜。冰的表面融化既具有根本意义，也具有重要的环境意义。冰与多种固体一起在其表面经历融化或无序转变。引起这些变化的基本机制、过渡层的特性以及它们对衬底的化学和形貌的依赖是有争议的。拟议的研究将寻求通过组合技术，特别是中子衍射和准电子中子散射来确定这些特征。表面效应和量子效应的共同作用可以将分子氢的熔化温度降低到7.2K以下。这种效应的研究对于理解量子流体和不同材料的固液界面具有重要意义。这项拟议的研究重点是用准弹性中子散射来表征表面熔化的液体，这是对华盛顿大学目前正在进行的热力学测量的补充。这项研究将受益于两组调查人员的互补专业知识。Dash、Vilches博士和他们的学生在吸附薄膜及其表面的研究中发挥了领导作用，特别是通过热力学技术。Bienfait博士和Suzanne博士在这些相同系统的研究中发挥了相当重要的作用，但主要是通过散射技术。

This award will support collaborative research in low temperature physics between Drs. Jay Dash and Oscar Vilches and their students, University of Washington, and Professors Michel Bienfait and Jean Suzanne, University of Aix-Marseille, France. The objective of the proposed project is to carry out studies of surface melting in crystalline systems. Two systems of particular interest are hydrogen dioxide-ice and thick physisorbed films of solid hydrogen isotopes. The surface melting of ice is of both fundamental interest and environmental importance. Ice undergoes melting or disordering transitions at its surfaces with many types of solids. The fundamental mechanisms which cause these changes, the characteristics of the transition layers and their dependence on the chemistry and morphology of the substrate are in dispute. The proposed research will seek to determine these characteristics by a combination of techniques, especially neutron diffraction and quasi-electric neutron scattering. The melting temperature of molecular hydrogen can be depressed to below 7.2 K by a combination of surface and quantum effects. The study of this effect is of major importance to the understanding of quantum fluids and solid- liquid interfaces of dissimilar materials. The proposed research focuses on characterization of the surface melted liquid by quasi elastic neutron scattering, complementary to thermodynamic measurements currrently underway at the University of Washington. The research will benefit from the complementary expertise of the two groups of investigators. Drs. Dash, Vilches and thier students have had a leading role in the study of adsorbed films and thier surfaces, particularly by thermoidynamic techniques. Drs. Bienfait and Suzanne have ha a comparably prominent role in the study of these same systems, but primarily by scattering techniques.