9422208 Hallock This proposal has four major points of emphasis: (1) To continue nuclear magnetic resonance and third sound studies of the helium3- helium4 mixture film system, specifically to study the strong effect on the helium3 of the helium4 film thickness with analogy with metal insulator transitions in 2D electron systems, and to search for transitions to new superfluid helium3 behavior which have been predicted. (2) To continue experiments with helium films on alkali metal surfaces in order to study wetting phenomena. (3) To study in more detail capillary condensation and avalanche phenomena with helium in porous materials. (4) To continue to study helium films patterned substrates in one and two dimensions. (5) To study linear and nonlinear behavior of third sound pulses in collision. The techniques used will include nuclear magnetic resonance, bolometric and quartz resonance and capacitance measurements. These experiments will develop our understanding of the helium film system and have impact more widely in Condensed Matter Physics. %%% This program will undertake a fundamental investigations of thin films of liquid helium which form on surfaces at extremely low temperatures. These films, which can be a few atoms thick, have remarkable properties and allow the study of physics in two dimensions which have implications for physics in other areas of Condensed Matter Physics. The emphasis will be on studies of mixtures of the two types of helium in which new types of superfluid behavior will be searched for. Analogies with metal insulator transitions will be explored. Peculiar wetting behavior between helium and certain unusual surfaces will be investigated. Capillary condensation and other phenomena in porous materials flooded with helium will be studied. The program will also investigate the interaction between microscopic waves on helium films and between such waves and th e surface on which they reside. ***
