Adsorption on Weak Binding Substrates

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9223775 Taborek This research project focuses on fundamental studies of adsorbed films of hydrogen, helium and neon on alkali metals and frozen hydrogen. The binding between the films and the substrates is weak, and as a result the adsorbed films display phases and phase transitions that do not occur on strong binding substrates (where the binding energy of the first few layers of adsorbate to the substrate is larger than the binding energy of the adsorbate to itself). Theoretical analysis indicates that these systems represent the entire range of weak binding behavior. The emphasis will be on the determining the dependence of features of the prewetting phase diagram on the adsorbate-substrate and adsorbate- adsorbate interaction parameters and on understanding the interplay between prewetting and bulk phase transitions, inducing superfluid onset in helium and the triple and critical points for the classical systems. The predominant technique will be the measurement of adsorption isotherms using microbalances supplemented by calorimetry and third sound. %%% The behavior of adsorbed films of liquid on solid surfaces is of interest from both fundamental and technical viewpoints. The study of the behavior of liquid films as they wet surfaces is complicated by the presence of various impurities at normal temperatures. This research will investigate the wetting of a range of surfaces by helium, hydrogen and neon. These films require ultralow temperatures, where impurity effects are essentially absent. The research will test recent theoretical predictions that suggest that the surface behavior of the various films will include unusual phase transitions that can be investigated by sensitive calorimety and microbalance techniques. The research will test these theories and potentially lead to films with new properties that may suggest new technological applications. ***