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

该奖项将支持低温物理学博士之间的合作研究。华盛顿大学的Jay Dash和Oscar Vilches及其学生，以及法国艾克斯-马赛大学的Michel Bienfait和Jean Suzanne教授。拟议项目的目标是开展晶体系统表面熔化的研究。我们特别感兴趣的两种系统是二氧化氢冰和固体氢同位素的厚物理吸附膜。冰的表面融化既具有根本意义，又具有环境重要性。冰在其表面与许多种类的固体发生融化或无序转变。引起这些变化的基本机制、过渡层的特征及其对衬底化学和形貌的依赖存在争议。提出的研究将寻求通过结合技术，特别是中子衍射和准电中子散射来确定这些特征。通过表面效应和量子效应的结合，可以将氢分子的熔化温度降低到7.2 K以下。这一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。提议的研究重点是通过准弹性中子散射来表征表面熔化液体，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研究人员的互补专业知识。Drs。Dash， Vilches和他们的学生在吸附膜及其表面的研究中发挥了主导作用，特别是通过热力学技术。Drs。Bienfait和Suzanne在这些相同系统的研究中发挥了相当突出的作用，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.