Monolayer Physics

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w:\awards\awards96\*.doc 9623395 Vilches This project is concerned with the study of surface and interface phenomena in H2, HD, D2, 3He, and 4He. A search for a liquid phase of H2 below 5.7K, the lowest triple point on record, will be conducted. Should a liquid phase be observed down to 2K or so, superfluid properties are expected. A careful survey of freezing and possible phase separation in H2-D2 film mixtures (and comparison studies with 3He-4He mixtures) will be done. Measurements of the frost heave pressure of H2 condensed inside micropores, where a surface melted layer of H2 should respond to a temperature gradient along the sample by sustaining a very large pressure gradient, will be performed. Neutron and X-ray scattering measurements on the various hydrogen isotopes will measure structure and transport properties. Graduate and undergraduate students are involved in all aspects of the project. %%% This project will explore, using different conditions and techniques, the possible existence of liquid hydrogen films to very low temperatures. Films of hydrogen formed on special solid substrates and hydrogen frozen inside porous materials may yield liquid films which will have unusual new fluid flow, heat transport, and/or pressure gradient properties. The technical side of the project will measure liquid and solid properties through thermal, pressure gradient, neutron, and X-ray experiments on the stable molecules of hydrogen, deuterium, and deuterium hydride, and their mixtures. Comparison experiments will be done using helium isotopes which are known to be fluid. Graduate and undergraduate students are involved in all aspects of this project. ***