Physisorption Studies

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To study thermodynamic properties of multilayer films of various adsorbates on uniform surfaces of graphite and other substrates. The technique, currently used by them and by one group in Germany, combines ellipsometric measurement of coverage with vapor pressure measurement by conventional capacitance manometers or by modified manometers operating at low temperature adjacent to the sample. Among the phenomena which will be studied are surface roughening and surface melting behavior of krypton, xenon, and methane films on graphite, including detailed examination of the layer critical points and inverse critical points which occur in fourth and higher layers, at least for krypton; exploration of the phase diagrams of neon and hydrogen in the same thickness range; and wetting and layering behavior of other interesting systems, such as carbon monoxide on graphite. Other substrates will be examined besides graphite, including TiS2, TaSe2, and other layered dichalcogenides, cleaved surfaces of ionic crystals such as LiF and MgO, and gold films evaporated on mica. A number of improvements in the experimental apparatus will allow better precision in coverage and pressure measurement.